TypeII-2 TypeII-1 TypeI-2 Olafs Simulator

The CURTA Calculator Page

"The world's first, last, and ONLY, mechanical handheld pocket calculator.*"

(since April 22, 1997)

Last Update: October 18, 2020 -- THE CURTA REFERENCE


   o The Curta Poster
Owners Registry
   o Curta Registry
Curt Herzstark
   o Curt Herzstark
   o Curt Herzstark Interview
   o Curta Backup Article
   o Miniature Machine
   o The Curious History
   o Curta Articles
   o Pocket Calculators
   o Curta: Rally
Curta Simulators
   o Olaf Veenstra's
   o Jan Meyer's
   o Pat Belford's
   o Curta Stats
   o Curta: Oldest
   o Curta Date
   o Curta Variations
   o Curta Manual
   o Curta Dimensions & Timing
   o Curta Service Manual
   o Curta Lubrication
   o Curta Factory Drawings
   o Curta Tools
   o Curta Disassembly
   o Curta Patents
   o Jack's Curta Repair (US)
   o Hans' Curta Repair (Europe)
   o Romano's Curta Repair (Italy)
   o Curta: The Ayen Collection
Curta Pictures
   o Curta Photos
   o Curta: Ray Traced
Curta Demos
   o Curta Demos
   o Curta: Cut & Special
   o Curta Prototypes
Curta Literature
   o Curta Ads
   o Curta Documents
   o Curta E-mails
   o Curta Literature
Curta Other
   o Curta Pins
   o Curta Museums & School
   o Curta: Media
        - Books
        - Stamp
        - Audio
        - Video
Curta Links
   o Curta Links


(click here)

(click here)

Introducing the classic Curta Calculator poster for all Curta fans. This fabulous poster shows a detailed layout of the inner working of Curt Herzstark's amazing machine. All Curta parts are close to actual size and displayed in multiple exploded views. Every part is labeled with its original name as designated in the Contina A.G. factory service manual. The elaborate and detailed poster design was nearly a year in planning and execution. Original factory photographs, drawings and artwork have been combined with new imagery to produce this engineer's view of a mechanical masterpiece. Many thanks are due to Carl and Jack for their encouragement and enthusiasm.

The Curta Calculator poster is very suitable for framing and will make a wonderful gift to any Curta enthusiast. It is an essential element in any Curta collection.

The poster measures 24 1/2" (62cm) in width and 16" (41cm) in height and is printed on high quality Strobe Gloss 100# cover paper. The poster will be shipped in a rugged 3" x 18" Kraft Mailing tube.


(click here)

The Curta Calculator poster printed in the German words of the Great Master, Curt Herzstark.

Introducing the classic Curta Calculator poster in German. Like the original Curta poster, this fabulous poster shows a detailed layout of the inner working of Curt Herzstark's amazing machine. All Curta parts are close to actual size and displayed in multiple exploded views. Every part is labeled with its original name as designated in the Contina A.G. factory service manual. The elaborate and detailed poster design was nearly a year in planning and execution. Original factory photographs, drawings and artwork have been combined with new imagery to produce this engineer's view of a mechanical masterpiece. Many thanks are due to Hans-Rudolf Roshard for his help translating this poster to German.

The Curta German Calculator poster is very suitable for framing and will make a wonderful gift to any Curta enthusiast. It is an essential element in any Curta collection.

The poster measures 24 1/2" (62cm) in width and 16" (41cm) in height and is printed on high quality Strobe Gloss 100# cover paper. The poster will be shipped in a rugged 3" x 18" Kraft Mailing tube.

(click here)

Buyer Feedback!

  • The poster arrived yesterday and it's terrific!   You did a really great job on it and I'd think any Curta collector will want one too.   What a great idea you had and thanks again so much for creating it. -- Greg -- Hillsboro, Oregon   USA

  • The poster was received today in perfect condition.   I thank you for your prompt and friendly service.   I'll be framing it and hanging it in my den. -- Jim -- Beachwood, Ohio   USA

  • Thanks!   This will hang in my office at NASA.   I have a Curta that I inherited from my great Uncle. -- Donald -- Huntsville, Alabama   USA

  • I received it a couple of days ago... Thank you!   It's wonderful!   Now I just have to find a frame and it will hang in pride of place in my house. -- Cath -- Bedfordshire, United Kingdom

  • Your wonderful Curta poster arrived well yesterday.   Thanks and best regards from Germany. -- Hermann -- Bayern, Germany

  • I have received the wonderful curta poster and I am inspired.   I congratulate you too this excellent poster. -- Bernd -- Langerwehe-Schlich, Germany

  • I received the Curta poster and it is beautiful to my eyes.   Even the sturdy custom mailing tube is a keeper.   I have the poster displayed temporarily in a poster frame with a thin plastic cover until I have a permanent frame made for it. -- Robert -- Alpine, Texas   USA

  • Hi Rick.   Just a quick note to let you know the Curta poster arrived today.   I am VERY pleased with it and plan to frame it for my office.   Thanks again! -- Sam -- Ridgecrest, California   USA

  • Rick - the Curta poster is absolutely fabulous, both the production quality and the concept.   It's something NO Curta Home should be without. -- Skip Godfrey -- Billings Montana   USA

  • Hi Rick, thanks a lot, I just received the poster!   It is fantastic, really well done.   Greetings from Madrid, Spain -- Angela

  • Speedy, secure shipment of an excellent product.   Great gift!   Thanks.   A+++ -- Bruce -- Okemos, Michigan   USA

  • The Curta poster is great.   I'm very pleased.   Sent quickly, too.   Thanks! -- Paul -- Hartland, Michigan   USA

  • Really beautiful item.   Really fast ship.   Thanks for a perfect transaction!! -- Kerry -- Sayre, Pennsylvania   USA

  • Excellent item, fast ship and well packed A+++++ -- Brian -- Lawrence, Kansas   USA

  • Thanks for the poster that I just bought.   It is great. -- Mark -- Santa Clara, CA   USA

  • Hi Rick, Received the poster today.   BEAUTIFUL!!!!   I left very positive feedback.   Thanks again -- Tom -- Stoughton, Wisconsin   USA

  • Hi Rick -- Beautiful job on the poster!   'twill be framed soon. -- Larry in Springboro, OH   USA

  • The Curta poster is wonderful!  Thanks so much.   --   Pam - Tucson, AZ  USA

  • Hi Rick, The poster arrived today—it’s fantastic!  Absolutely beautiful!  Thanks, Bob - Palo Alto, CA  USA

  • Rick, Your work is outstanding!  The poster is amazing; I've been studying it since it arrived.  The detail and quality of the photos is excellent and the amount of data you have included is impressive.  I noticed your name in the CURTA article in the January [2004] Scientific American (in the box on page 98 where the author, Cliff Stoll, thanks his elves) and now I know the source of some of the photos in the article since I visited your web site. -- Charlie -- Randallstown, MD   USA

  • Rick, I got the poster and my engineer colleagues come to my office just to study it!  Ray - North Bend, WA  USA

Countries Sold To (so far)

  • AE - United Arab Emirates
  • AR - Argentina
  • AT - Austria
  • AU - Australia
  • BE - Belgium
  • BR - Brazil
  • CA - Canada
  • CH - Switzerland
  • CO - Chile
  • CL - Colombia
  • CZ - Czech Republic
  • DE - Germany
  • DK - Denmark
  • DM - Dominica
  • EC - Ecuador
  • ES - Spain
  • FI - Finland
  • FR - France
  • GB - United Kingdom
  • GP - Guadeloupe
  • GR - Greece
  • HK - Hong Kong
  • HN - Honduras
  • HU - Hungary
  • IE - Ireland
  • IL - Israel
  • IN - India
  • IT - Italy
  • JP - Japan
  • KR - Korea, Republic of
  • LI - Liechtenstein
  • LU - Luxembourg
  • MX - Mexico
  • MN - Mongolia
  • NE - Niger
  • NI - Nicaragua
  • NL - Netherlands
  • NO - Norway
  • NZ - New Zealand
  • PH - Philippines
  • PL - Poland
  • PR - Puerto Rico
  • PT - Portugal
  • RU - Russian Federation
  • SA - Saudi Arabia
  • SE - Sweden
  • SG - Singapore
  • TR - Turkey
  • TW - Taiwan
  • US - United States
      Every state except:
       o South Dakota!


    (click here)

    The Curta Calculator Patent Poster was created by Aaron from MuseumOfLyrics.

    This poster displays various detailed patent and engineering drawings of the Curta Calculator.

    The poster has been created for A1 printing and is highly detailed, however it would look fine as A2. A3 would be fine but the drawings would look small.

    This is a Digital File only and is for sale on the Etsy web site. https://www.etsy.com/listing/711993137/curta-calculator-patent-poster

    Click here

    The CURTA Collectors and Registry Page

    Over 800 CURTA Owners and close to 1,000 Curtas!

    Last Update: November 2017

    The CURTA Collectors and Registry Page is a list of people who collect/own/like CURTAs!

    CURTA Stats

    Curt Herzstark

    POB: Vienna, Austria
    DOB: January 26, 1902
    DOD: October 27, 1988
    Parents: Samuel Jakob Herzstark [b.October 10, 1867 in Vienna d.October 24, 1937]
    and Marie Herzstark [d.January 1956]
    Grandfather: Benjamin Herzstark from Danzig [Poland]
    Fathers Business: Austrian Calculating Machines Manufacturing Company, Vienna f.1905
    Production was started at April 1, 1947.
    In 1966 CONTINA AG was bought by the firm HILTI AG in Schaan.
    Production was stopped on November 1970.
    CURTAs were sold until early 1973.
    There are +/- 80000 Curta I and +/- 60000 Curta II machines.
    Curt Herzstark heard 150,000 to 160,000, maybe even more CURTAs were manufactured.

    Type I

    Type II

    POB:Mauren, LiechtensteinMauren, Liechtenstein
    DOB:April 1, 19471954
    DOD:November 19701954
    Sold Till:19731973
    Capacity:8 x 6 x 1111 x 8 x 15
    Parts:~600, 139 unique~719
    Weight:8oz - 230g, 244g (measured)12 1/2oz - 360g, 372g (measured)
    Diameter:2 1/16" / 2.08" - 53mm2 9/16" / 2.56" - 65mm
    Height:3 3/8" / 3.35" - 85mm3 5/8" / 3.54" - 90mm
    Height w/crank:4.21"/107mm4.38"/111mm
    Case:4.73" x 2.40" - 120mm x 61mm5.13" x 2.88" - 130mm x 73mm
    Total (Curt estimate):80,00070,000
    Total (factory record):80,42761,660
    Total (pictorial evidence):79,21861,061
    Total (estimated):79,32069,942
    Oldest (pic):000968500002
    Oldest (registerd):2044500084
    Newest (pic):80186561063
    Newest (registered:80288569944
    S# on top start:38210N/A
    S# on top end:40469N/A
    Black body end (pic):N/A510348
    Black body end (registerd):N/A510395
    Gray body Start (pic):N/A510536
    Gray body Start (registerd):N/A510633
    Metal can end:47753532716
    Plastic can start:49815532511
    Notes: 1- 7178 then a few more pin sliders were produced from 9321-9620.

    Type I's with Serial Numbers on top row of bottom plate (most Curta's have the serial
    number on the bottom row of the bottom plate).
    37840 (does not have SN on top)
    oldest picture: 38600
    newest: 40469
    41416 (does not have SN on top)
    It appears that at least a little over 1800 units (out of 80,000) have the serial number
    on the top row of the bottom plate.

    Production in 1949 about 300 to 400 per month; in 1952 about 1000 per month
    In 1949, only 300 CURTAs were made each month.
    By 1952, 1,000 CURTAs were made each month.
    CUTRA 2s started at serial number 500,000.
    The black type II case ended between 510348 and 510536.

    The only way 540331 could be black would be if the bottom plate was switched or
    the calculator was assembled out of spare parts.

    Oldest Curta

    The Oldest Known Curta

    This page contain pictures of the oldest type I and type II Curtas. If you own a really old (or really new) Curta then send me your pics and I'll add them to this page if they qualify.

    CURTA Serial Numbers
    Click here

    CURTA Date by Serial Number


    CURTA Production Date by Serial Number contains a discussion and two formulas to calculate approximately when your CURTA was made.

    Here's a great article from Daniel F F Ford with a more precise method to determine the Curta's age: When was your Curta made?

    Curta Manufacturing Evolutions

    Demo Curta Demo Curta
    Demo Curta Demo Curta

    Above are three different styles of type 1 Curtas.
    Notice the difference between the handle top, the entry knobs,
    the labeling/lettering, and the storage cans?

    Model Variations

    serial # can crank body top decimal bottom decimal clearing ring entry levers
    type I Curta 5 3
    2185 metal metal black 5 3 metal pin
    5790 metal metal black 5 3 metal pin
    7278 (was 9897) metal metal black 5 3 metal rectangle
    13836 metal metal black 5 3 metal rectangle
    15045 metal metal black 5 3 metal rectangle
    52335 metal plastic black 5 2 metal rectangle
    58562 metal plastic black 5 2 metal rectangle
    74738 plastic plastic black 5 2 plastic rectangle
    type II Curta 6 3
    504094 metal metal black 6 5 metal rectangle
    526699 metal + leather plastic grey 6 3 metal rectangle
    541431 plastic plastic grey 6 3 metal rectangle
    557788 plastic plastic grey 6 3 plastic rectangle

    Curt Herzstark - The Man

    Thanks to Prof. Karl Kleine from Jena, Germany, Curta.org and Curta.li for some of these pictures. If you have any other pictures of Curt send them to me. -Rick-

    CBI Logo CBI Header

    An Interview Of CURT HERZSTARK From 1987
    (now available as a local .pdf copy)

    This is a wonderful document. A must have for all CURTA enthusiasts! -Rick-

    Curt Herzstark, OH 140. Oral history interview by Erwin Tomash, 10 September 1987, Nendeln, Liechtenstein. Charles Babbage Institute, University of Minnesota, Minneapolis.

    Herzstark, an Austrian inventor and manufacturer of calculators, describes the development of the Austrian Calculating Machine Manufacturing Company (Rechenmaschinefabrik der Austria Erstanden Compagnie) and his subsequent work in the industry. The company, founded in Vienna by his father, Samuel Herzstark, in 1905, introduced the first electrically-driven calculator based on improved designs of the Thomas Arithmometer. Herzstark describes the disruption of the industry during World War I, his involvement with the company after the war, competition with American companies, and his first invention, a mechanical memory for holding subtotals, which appeared in 1928. Herzstark managed the company in 1930 and began work on his own design for a hand-held calculator. With the Anschluss of 1938, the company was again converted to war production, and produced custom gauges for German tanks. Herzstark, a Jew, was able to avoid arrest until 1943, when he was sent to Buchenwald concentration camp and worked as a technician. He recounts his arrest and internment, and how he completed the design of the CURTA hand-held calculator, a prototype of which was produced in Weimar, Germany, by Rheinmetallwerke at the end of the war. The Prince of Liechtenstein bought the design and the calculator was initially manufactured by the CURTA division of Contina AG of Liechtenstein. It was produced until 1972, when the electronic calculator forced it from the market.

    The transcript is available in English and German, and can also be downloaded from the CBI web site.

    Backup Curta
    Click here

    Curt Herzstark and his Pocket Calculator CURTA.

    A good article from backup magazine 6/88 page 5-9 and 1/89 page 41-45

    This artice was translated by Andries de Man -- Thanks Andries!

    CURTA Articles

    The CURTA Articles page is where you will find interesting articles written about the CURTA.

    Curta Mechanism
    Click here

    Miniature Machine Performs Engineering Calculations

    A really good CURTA article from Product Engineering magazine -- October 1952.

    Click here

    Pocket Calculators Then and Now

    This issue of the Report is based on an exhibit that allows you to journey through the history of the pocket calculator. You will meet the people who have used pocket calculators in the past and discover the problems they solved. At the exhibit you can try your hand at using their calculators. While in this publication, you will leam more of the anecdotes associated with the artifacts. Gwen Bell
    (published by Computer Museum History Center, Winter 1987)

    Click here

    THE Curious History of the First POCKET CALCULATOR

    The Curious History of the First Pocket Calcualtor by Cliff Stoll. It was called the Curta, and it proved lifesaving when its inventor was trapped in a Nazi concentration camp.
    (published by Scientific American, Jan 2004)

    Click here

    The Curta Calculator by Jim Bianchi

    Curta Mechanical Calculator as used in TSD rallying by Jim Bianchi
    (as published in rallye magazine, March 1976)

    Olaf Veenstra's Amazing Curta Simulator!

    YACS - Yet Another Curta Simulator

    A complete "Mechanical" Curta simulation. Watch every major part of the Curta turn and interface with it's mating piece.

    Now you can see the step drum perform it's 10s complement magic, the gears turn, the transmission shafts rotate, the carry levers shift, and the digits count.

    Spin it, flip it, zoom in, zoom out, explode it. Turn the crank slow, turn the crank fast.

    Watch it operate in any position or view angle!

    What would Curt Herzstark have thought! Amazing!

    This is the new granddaddy of the Curta Simulators and must be tried!


    This model needs the Bitmanagement VRML viewer. It's free, safe and never expires. Installation instructions are available at The YACS Homepage

    A sample of the Curta Simulator is featured on the Bitmanagement Website

    Visit Olaf Veenstra's web page: YACS - Yet Another Curta Simulator

    Jan Meyer's Fantastic Curta Simulator!

    Click here

    The Curta Simulator I

    A complete Curta simulation, with which all arithmetical examples can be accomplished.

    You don't have a Curta? Then you can use the Curta simulator .

    It needs Flash Player 6, which you can download here free of charge.

    Visit Jan's Curta Web page: www.curta.de

    Pat Belford's Curta Simulation and Manual

    Click here

    The Curta Simulator II

    A complete Curta simulation, with which all arithmetical examples can be accomplished.

    The Curta Calculator simulation is a 3D re-creation of the original portable mechanical calculator, invented by Curt Herzstark. Unlike modern electronic calculators, the Curta was entirely mechanical. It could add, subtract, multiply and divide, and unlike other calculators of the day, it could fit in your pocket.

    It needs Flash Player 6, which you can download here free of charge.

    Visit Pat's Web page: www.patbelford.com

    Your Curta
    Click here

    The CURTA Manual

    The CURTA Manual is a transcription of the CURTA Manual titled "Your CURTA Calculator" on one side and "The 4 arithmetical rules" on the other. Pictures are now included.

    Here's a printable pdf version: Your CURTA Calculator.pdf

    The same CURTA Operating Manual rendered simultaneously (CURTA ESP) by Andries de Man.

    A French CURTA manual created by Philippe DAILLY.

    A French CURTA manual translated by Andries de Man.

    A second French CURTA manual translated by Andries de Man.

    Curta Timing and Dimensions

    (click here)-Curta Timing (click here)-Curta Subtract

    (click here)-Curta Dim 2 (click here)-Curta Dim 3

    Original Curta Service Manuals

    (click here)-Curta I Service Manual (click here)-Curta II Service Manual

    These manuals are from the wonderful Museum Mura. Unfortunately they are in German. Also see the assembly video (in my Video section below).

    Original Curta Factory Drawings and BOM

    (click here)-Curta I BOM (click here)-Curta II BOM

    (click here)-Curta Drawings
    (58.5M download)

    These files are from the wonderful Museum Mura. Also see the assembly video (in my Video section below).


    CURTA Cleaning and Lubrication

    I get asked all the time about how to clean and lubricate the Curta.
    Click on the Lubrication image for some helpful email snipets from Nicholas Bodley and Jack Christensen plus some scans from the Curta Service Manuals.

    Disassembly Disassembly

    The Curta Disassembly

    Well I finally did it. Thanks to the support of my friend Carl I fully disassembled a type 1 Curta. The really good news is I put it back together and it still works! This page is BIG so go here only if you have a high speed connection or the time to spare. Each picture can be clicked on for a larger view too. -Rick-

    Curta Tools
    Click here

    Curta Tools

    Ever wonder how to work on a Curta? To do it right your need many specialized tools. Here are some of them from the collection of Hans-Rudolf Roshard.

    CURTA Patent

    CURTA Patents

    I have discovered a total of 60 CURTA patents!

    Curt was also assigned at least 19 patents related to various manufacturing processes and devices (sorry, I don't heve these published).

    And 12 patents by Kurt Herzstark's principal engineer Mr. Elmar Maier.

    I also have found 37 patents assigned to Curt's father [Samuel Jakob Herzstark] dealing with adaptations, additions and improvements to the Thomas calculator (sorry, I don't heve these published either).

    Demo Curta Demo Curta Demo Curta Demo Curta Demo Curta Demo Curta

    Curta Prototypes

    Details of these early prototypes can be seen in some of Curt's patents.

    The last two pictures are of a type 1A prototype (notice the serial number... 100049)

    Some Nice Curta Photos

    Demo Curta Demo Curta Demo Curta
    Here are some nice pictures I found on the Internet. (Click on the picture to open the page)

    HGA Curta
    Click here

    The Helmut G. Ayen Collection

    The Helmut G. Ayen Collection Page is a set of 33 beautiful pictures that I was sent from Helmut Ayen in Hossingen, Germany. He not only owns a pair of type I and type II Curtas but also a pair of type I and type II Demo Curtas! Enjoy the pictures and as always, click on any picture to get a larger version.

    Ray Traced Curta
    Click here

    Curta Type II Ray Traced Picture

    Here is a great picture created by John Cherry. He was learning to use ray tracing software (POV-Ray 3.02). This is a picture of his Curta Type II (number 546692).

    The picture uses 16 Million colors.

    There are equivalent versions of POV-Ray for MS-DOS, Windows 95/98 & x86 NT, Macintosh, PowerPC, Amiga, SunOS, Linux (on Intel platforms) and generic Unix.

    Great Job John!

    Cut Curta
    Click here

    Special Curtas

    Here is a large selection of special Curtas. Many of the pictures are from the collection of Hans-Rudolf Roshard.

    The Skeleton Curta belongs to Richard Moor. He worked for Victor Comptometer, in Chicago, in the Research Center, as Prototype Model Maker from 1967-1976.

    There are 3 cut-out "windows" on the clearing plate, 3 long "windows" on the upper knurled ring, 4 long "windows" on the lower knurled ring, 6 "windows" on the bottom plate, and the middle portion of the unit is open. All of the Lettering, Numbers and Arrows have been left INTACT, and the Little "rechnende Mocca-Mühle" is still fully functional.

    The picture of a chrome Curta is from Stephan Weiss.

    According to Reinhold Rehbein, the history says that, a short time before the factory in Lichtenstein was closed, Curtas were made from different spare parts. Almost every old Curta factory machinist has made a variant.

    Demo Curta
    Click here

    The CURTA Demo Collection Page

    The CURTA company produced demo units for their sales force. According to a conversation with a factory trained repair technician, they only produced one demo unit per country that the Curta was sold in. If you own a Demo unit, send me a picture and I'll register it on the Curta Demo page.

    Curta Pins

    Curta Pins

    These pins were made for an annual collectors meeting in Liechtenstein.

    Thanks to Skip Godfrey for sending these pins to me.

    I'd be real interested to learn if there were any other pins made and if there were more pins I'd like to get a picture to put on the web site. I'd like to know more about the annual meeting... email me with info... Rick Furr (rfurr(at)vcalc.net)

    Curta Pins Curta Pins
    photo from Jay K. Jeffries

    Curta's in Museums & Schools

    This page contains pictures of Curtas that are on display in museums around the world. If you find any new museums/pictures send them to me and I'll add them to this page.

    Curta Key
    Click here

    CURTA Literature Listing

    CURTA Literature Listing is a list of all know CURTA literature compiled by Rick Furr and Skip Godfrey. Please send us copies of your literature if it is different so we can include it.

    CURTA E-mails

    The CURTA E-Mails page is a set of interesting E-mails distributed by Erez Kaplan's Calculating Machines List server.

    Ad-All Purpose
    (Click Here)

    CURTA Ads and Magazine Blurbs

    These CURTA Ads were from Scientific American, June 1961 and June 1971 respectively.

    Click here

    Update - I talked with Jack and he's over a year behind in repairing CURTAs.
    I don't recommend you send him your Curtas until further notice. -Rick-

    Here are a few questions I asked Jack:

    What do you charge to clean a Curta?

    Typically $115 to $280, depending on the type of Curta [Type I or Type II] and the work involved. In those situations where only the upper carriage or the main body needs work, the fee will be at the lower end of the price range. More often than not, the entire machine needs a complete disassembly. It is my preference to thoroughly clean everything, so the charges are usually toward the upper end of the price range. If a full restoration is needed, the cost may even be higher. If something internal is bent, out of adjustment, or broken, the entire machine usually needs a complete disassembly.

    What do you charge when repairing a Curta?

    I charge $65 per hour of my time. It seems my hours are about 90 minutes long, however, because I rarely finish in the time I originally quoted. Extended repair time is absorbed by me.

    What spare parts do you have? Are they expensive?

    I actually have many hundreds of new original Curta parts. Most are for inside the instrument, though. I use them when I do general cleaning and repairs. Outer body pieces, replacement cannisters, and external parts that are easily damaged or broken due to abuse are not generally available, although I do occasionally locate some these items. Sometimes I have to fabricate a part, or repair an item as best I can. Obviously, this takes time, and the cost is high.

    Parts costs are charged as the traffic will bear. I usually try to be blunt about this to the Curta owner, often telling them that a severely damaged unit is best sold as a "parts Curta". Unfortunately, I've sometimes had to tell this to someone who wanted to repair a Curta looked upon as an heirloom. What to them appears to be a minor issue actually turns out to be a major problem (e.g., a crank handle tilted downward is due to a broken main shaft).

    Costs for both a cleaning and typical repair is often between $150 and $250. I think the most I ever charged for a repair was about $500...there were many serious problems with the machine. Generally, when the price gets to be above $300 many people simply keep the damaged Curta as a memento.

    Can you replace a clearing ring? What costs are involved?

    Plastic clearing rings are available. I have several new ones, but I typically do not sell them separately as a spare part. Rather, I install them during a general cleaning and repair. I can modify a Curta that originally had a metal clearing ring to allow a plastic clearing ring to be used. There are special rivets for this purpose, which I have.

    Metal rings are more difficult to replace. As with the plastic clearing rings, I will only install a metal clearing ring during a general cleaning and repair. It takes a special tool to properly swage the rivet in place. [Editor's note: Very old Type I clearing rings were held on with a screw and nut. The nut was crimped to the screw threads below the clearing plate. Don't turn the screw! You'll break the screw and/or strip its threads!] I have only a very few new metal clearing rings for both the Type I and the Type II. I also have used metal clearing rings [that were removed from damaged Curtas] for both the Type I and the Type II. The new Type I metal clearing levers are so rare that I will only install the ones I have on very old or very special machines. The cost for a new Type I clearing ring is extremely high. The rivets needed to install a clearing ring are special too, but I do have a few.

    Jack's company, Timewise also manufactures a line of rally equipment for TSD competition. The units include TSD computers for running in a Computer Class, units designed for Odo Class competition, and competition and checkpoint clocks. Jack can be contacted for special-order equipment or particular modifications desired for Timewise equipment. Jack also repairs older Zeron equipment. A wide selection of sending units are available.

    Jack Christensen
    32 Old barn Road
    Hawthorn Woods, Illinois 60047
    (847) 550-5052 (evenings)


    Cleaning of CURTA Calculators

    Would you like to have your CURTA calculator revised or cleaned or it doesn't work properly?

    I would be glad to submit you an quote. I can repair, clean and revise your CURTA calculator with original instruments and spare parts.

    I also buy broken and functioning CURTA's as well as spare parts.

    Hans-Rudolf Roshard
    Schöntal 10
    CH - 8126 Zumikon
    Tel. +41 44 918 09 86
    E-Mail roshard(at)bluewin.ch


    Hans is a friend who lives in Switzerland. He is an expert with the Curta.

    August 19, 2015 - I just received a eMail from Hans. Hans has had some family issues to deal with over the past year and has not been able to dedicate any time to repairing and servicing Curtas. The good news is things are better and he is now able to begin working on Curtas again! He has one of the largest remaining inventories of Curta parts and tools and your Curta will be in good hands! -Rick-


    Click here to visit www.curtaservice.it

    If your Curta is damaged or if it doesn’t work correctly, if it needs revising or just cleaning and you want it back working and in perfect shape, this is the right website for you.

    We repair, calibrate, tune, revise and clean these mechanical wonders. We have been doing this for years for a limited group of collectors, but now we have decided to start operating on an international level.

    You can send us your Curta and, completely free of charge, we will let you have our estimate of the costs of our service. As an alternative, we will assess the value of your Curta (whatever its condition) as a firm offer to buy it from you.

    If you are not willing to accept our proposals, we will send your Curta back to you, without any further cost on your part.

    As you have certainly noticed from our simple and essential website, we do not intend to impress anybody with special effects: we just work hard and seriously, and we guarantee the results of our work.

    If you need any further information or if you have any doubt or question to ask, do not hesitate to contact us: info@curtaservice.it

    Ravenna, Italy, September 2010

    CURTA Media

    CURTA Calculator: The Handbook

    A New Concept for Using the CURTA Calculator

    It is a true "modern tribute to the genius of CURTA"

    With its visual algorithms in the form of tables, the calculation sequences become attractive, and of an exceptional aesthetic presentation. The pleasure of using the CURTA is multiplied. It includes the amazing possibility of CURTA to quickly calculate the area of any polygon. It also includes some new algorithms such as a succession of magic numbers as well as the golden number or the date of birth of any CURTA calculated by the machine itself !

    21 remastered algorithms:

    o Addition - Subtraction
    o Multiplication - Division
    o Division by breaking down
    o Continued multiplication
    o Rule of three
    o Simultaneous calculations
    o Square root
    o Power calculation
    o Pytagoras’ theorem
    o Area of a polygon 1
    o Area of a polygon 2
    o Magic numbers
    o The phoenix
    o Lewis Carrol’s number
    o The golden ratio
    o Date of birth of a CURTA

    High quality of realization. An essential collector for any CURTA enthusiast.

    Available on eBay: https://www.ebay.com/itm/CURTA-Calculator-The-HANDBOOK/373169063239

    Curt Herzstark Book (in German)

    A book about Curt Herzstark "Kein Geschenk für den Führer" which means "No Gift for the Leader"

    Curt Herzstark Book (in English)

    This Oughtred Society’s translation of the autobiography of Curt Herzstark, the inventor of the CURTA calculator, is a must have for a CURTA collector or enthusiast. This book documents the life of Curt Herzstark, his youth in Vienna, his education and travels with his father (also an inventor of a calculating machine), his internment at the Buchenwald concentration camp, and his post-war difficulties in the production and distribution of the CURTA calculator. Additionally, appendices provided by Tom Wyman and Bob Otnes provide additional information about the use and derivation of the CURTA calculator. Many photographs are included.

    English, Perfect Bound, 8½" x 11", 180 pages, 20 ounces,
    $36.00 plus shipping.
    Order at www.oughtred.org

    Pattern Recognition Book

    The Curta is featured in the novel Pattern Recognition by William Gibson, where the heroine trades one of the first ever produced Curta for a valuable piece of information from a former spy who is now a collector of mechanical calculators.

    Postage Stamps

    "Technical innovations in Liechtenstein"
    The stamps were released in 2006 by The Liechtenstein Postal Service
    The series' technical innovations from Liechtenstein presents "inventions that were developed in Liechtenstein and conquered the world market. In the first two series, the Curta calculator, the camera Carena, the caliper of the PAV and the Hilti Hammer, Kaiser walking mobile excavators and the heating surface aluFer were presented by the Hoval.

    Design For The Real World by Chris Spurgeon - Audio

    This is an audio track by Chris Spurgeon about the Curta. It was broadcast by Studio360. The show is called "Design For The Real World".

    Cool YouTube Videos

    Curta Assembly Video

    Published on Nov 22, 2013
    Zusammenbau einer Curta Rechenmaschine
    Demonstration of CURTA calculator assembly
    CURTA was manufactured from 1949 to 1971 at Contina AG in Mauren, Liechtenstein
    CURTA history is displayed in the museum MuseumMura, 9493 Mauren, Liechtenstein
    Website www.museummura.li

    A Visual Guide to Mechanical Computing presents The Curta by Mike Hilton

    This is a great instructional video based on Olaf Veenstra's YACS VRML Simulator!

    The CURTA was featured on The History Channel's Pawn Stars on May 2nd, 2011

    The PawnStar's CURTA segment.

    Watch the segment: HERE

    The Assembly of YACS - Yet Another Curta Simulator by olafzijnbuis

    YACS - Yet Another Curta Simulator. A Guided Tour by olafzijnbuis

    The Astounding Curta Mechanical Calculator by rregister

    Curta mechanical calculator by Gyroscopes

    Square root of 2 using the odd subtraction method by HifiCentret
    Now go try Newtons method [ A=((N/A)+A)/2 ]...

    Links to other CURTA Calculator pages:

    * "The world's first, last, and ONLY, mechanical handheld pocket calculator." credit to Jim Chen, Fair Lawn, NJ!

    The Calculator Reference by
    Rick Furr (rfurr(at)vcalc.net)
    Back to The Calculator Reference