Uploaded February 2020 | Updated September 2026, 2 hours ago

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The Addometer was made by the Reliable Typewriter & Adding Machine Company from 1927 until the 1950s. It is an 8-digit dial adder with a built-in stylus and clearing mechanism. It also has an 11-inch ruler along the top.

For more information about this and other calculators in my collection, visit my website:
jaapsch.net/mechcalc

0:00 Introduction
0:55 Addition
1:29 Subtraction
2:01 History
2:42 Clearing
3:13 Instructions
3:29 Models
4:13 Opening case
6:00 Carry mechanism
7:35 Clearing mechanism
10:05 More history
12:14 Outro