Addometer Mechanical Calculator  
Written by AnubisTTP on 2021-06-12  



The Addometer is a small, handheld, stylus operated adding machine that was produced in large quantities during the first half of the 20th century. The machine consists of a set of 8 digit wheels encased in a long rectangular metal enclosure with carry levers located above each wheel. Using the machine for addition is very simple; the stylus is inserted in the hole for the desired number on each dial and turned clockwise to add it to the total, which appears in the small round windows at the bottom of each dial. The machine can also be used for subtraction, in this mode the dials are turned counterclockwise and the smaller numbers are used for input. A sliding lever on the side of the device can be pulled out to reset the machine to zero. The Addometer was manufactured for nearly 40 years starting in 1927, and as such is quite common in the collectors market.


Addometer Calculator Inside
Addometer adding machine with cover removed.

Addometer Mechanical Calculator
Addometer adding machine.

Addometer Teardown
With the cover removed the small plastic gears for the carry function can be seen.

Addometer Advertisement
A period advertisement for the Addometer.

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