The purpose of this site is to provide a repository of information about the Odhner pinwheel calculator. My interest in the subject began when, as a relative of the inventor (Great Grand Nephew?), I decided I would attempt to locate and purchase one for myself. When I saw pictures of some older models and read a little about the history, I was extremely impressed with both their elegance and their historical significance. Prior to the invention and mass marketing of the Odhner pinwheel calculator, scientists and businessmen simply had no way of quickly multiplying or dividing large numbers. There were various machines that came close, but they were both unaffordable, and incomplete in their capabilities. The Felt Comptometer (1885) was a similar huge step in technology, but it was an adding machine, not a four function calculator, and as such did not compete with the Odhner type pinwheel calculator, which dominated the four function calculator scene for many decades, from 1875 up until the arrival of the electronic calculators in the early 1960's. Depending on date of manufacture and condition, the value of an Odhner Pinwheel Calculator on the antique and collectables market ranges from $100 to $10,000, and in many cases they are now priceless museum exhibits. Early examples of Odhner types manufactured by other companies, notably Brunsviga, Marchant, Thales, Felix, Humann, Rapid, Walther and Triuphator, as well as many others, also have some value on the collectors market. These are virtually identical to Odhners and are based on the Odhner design. For this reason, I have had to equip myself with some difficult to obtain information in order to correctly identify and evaluate any machines which surfaced in auctions or elsewhere on the the antique market. I have now purchased two examples, an "Odhner's Arithmometer" made in Russia around 1906, and an "Original Odhner" made in Sweden around 1928. Hopefully, this site will make it a little easier for others interested in bidding on an Odhner to evaluate it.

The concepts behind this invention had been explored by De Vinci, Pascal, Liebnitz, Thomas and others prior to Odhner's invention of the first successful pinwheel calculator. For this reason, the real significance of Odhner's design was not so much the pinwheel principle itself, but his practical implimentation of it, along with a reliable automatic carry mechanism. There is a lot of scattered information on the internet, and in a few books, as well as in the heads of several collectors who know a great deal about these machines. I am hoping to gather a lot of this so it can be available in one spot. Eventually, I'd like to write or patch together some articles on the historical significance of this invention, put it in some context with the overall history of calculating, and even provide some personal history of the inventor, Willgodt T. Odhner. At this point, however, the site is mostly a collection of pictures I've found of Odhner pinwheel calculators intended to represent the design evolution over time. I have added comments focused mostly on the issue of determining the date of manufacture by identifying various features. Original Odhner also produced mechanical and electro-mechanical adding machines and calculators, (i.e. "10 key" calculators, etc.) however, this site is limitted to the pinwheel calculators otherwise known as the "Odhner type" calculator.

Formal manufacturing records from the Odhner company in Russia are thought to have been lost during the Russian Revolution, and thus there are no tables (as far as I know) which can conveniently index serial numbers according to date of manufacture. Therefore, all dating of the Russian made Odhner calculators must be derived analytically, by comparing the scant descriptions, photos, drawings, ads, and histories available to the features and the serial numbers of known models. I think there is enough information to piece together a database that will make it possible to assign a date to Russian made calculators with a reasonable level of certianty. As further information surfaces, the picture should become clearer. Most importantly, there are many people who already have knowledge far beyond mine, or may happen to have a particular piece of critical information, or own or know of a calculator which would add to, correct, or verify some of the guesswork shown below. I hope these people will support my effort by correcting my errors, and contributing whatever information they may have, including stories.

Although there is serial number to date information available for the Odhner calculators made in Sweden after 1917, it is rather weak for the ten year period prior to 1928, which simply says "below 70,000" for this reason, I am interested in fleshing out this period as well. Furthermore, I will be collecting information regarding the feature changes throughout the Swedish production, so that it will be easier to identify a calculator's age even without the serial number. All information is welcome.