Odhner-type calculating machine, 1910-1920.
© Science Museum / Science & Society Picture Library
Barrel calculating machines were smaller, lighter and easier to operate than their predecessors, Arithmometers. The machine performs multiplication by repeated addition and includes the wheel with a variable number of teeth as patented by Willgodt T Odhner (1845-1905) in 1891. Made by the Muldivo Calculating Machine Company and engraved 'Unis France, no 9697'.