Mechanical calculators were first developed to reduce errors made by human calculators – an asset that was valued in any business or institution that required reliable calculations.

This circular calculating machine was patented by Joseph Edmonson in England in 1883. Used for addition and subtraction, Edmondson’s circular calculator has a brass and steel mechanism housed in a wooden case. It was reliable and robust but it was a complex instrument to master. The operator had to know where and how to set the numbers to be used in the calculation, how to perform the function and where to read the result. These challenges created a barrier to its comprehension and operation.

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