Duplex Addiator
Made in Germany 1920s - 1930s. (Front: addition. Rear: subtraction), with stylus and case. 121 x 178 x 6 mm (4.75" x 7" x 0.25")
From "Calculating Machines & Instruments", Science Museum, London, about a similar 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."
