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Sterling currency Addiator.
121 x 178 x 6 mm (4.75" x 7" x 0.25").
Made in Germany 1920s - 1930s.
One side of the instrument is used for addition and the reverse for subtraction. The stylus advances each colmn by the number to be added or subtracted, with carry possible to the next column.
This type of calculator was introduced by the Frenchman Troncet in 1889. The Addiator was one of the most popular calculators of this sort, and the name is often used to refer to the type generally.
Although this model is a little large, these were the mechanical pocket calculators.
From "Calculating Machines & Instruments", Science Museum, London, about an exhibit there -
"Made and presented by Addiator Gesellschaft, Berlin.
This instrument, which shows the latest development of the Troncet type of arithmograph, was placed on the market in August 1920, and 100,000 examples were sold within a year. It is attractively
designed on mass production lines, and various models are made, adapted to different systems of coinage, weights and measures."
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