Odhner Arithmometer

The Odhner Arithmometer was a pinwheel mechanical calculator invented in Russia in 1873 by the Swedish immigrant Willgodt Theophil Odhner. Odhner conceived it in 1871 while repairing a Thomas Arithmometer, the only mechanical calculator in production at the time, and replaced that machine's heavy, bulky Leibniz cylinder with a lighter, smaller pinwheel disk, which is why the two machines share a name but look quite different. In 1876 he agreed to build 14 machines for his employer Ludvig Nobel and delivered them in 1877. He patented the original machine in several countries in 1878 and 1879 and an improved version in 1890, when serial production began in his Saint Petersburg workshop. In 1891 he opened a branch in Germany, which he sold in 1892 to Grimme, Natalis and Company, who made the machine as the Brunsviga. About 23,000 calculators were produced in Russia before the factory was nationalised and closed in 1918, but clones made by independent companies around the world kept the design in production into the 1970s, and by 1950 it was one of the most popular mechanical calculators ever made.