The Odhner arithmometer was a pinwheel/mechanical calculator invented in Russia in 1873 by Willgodt T. Odhner, a Swedish immigrant. Large scale manufacture of the arithmometer however only started in 1890 in the factory in St Petersburg. Towards the end of 1917, Odhner went back to Sweden and restarted the production of the calculator under the Original Odhner name. This particular arithmometer was made in Sweden evident from the engraving on its base, and is likely to be Model 239, as indicated by the first three digits of the serial number (also engraved on its base). The Odhner arithmometer marks a milestone in the development of calculators, and it was a popular mechanical calculator that even made its way to Singapore. Because it was less bulky, easy to use, affordable and reliable, it gained popularity until electronic calculators came onto the scene in 1970s.
