Lightning Adding Machine Sales Company Addometer
1950s

Frank Baldwin based his calculating machine on the invention of Gottfried Leibniz, the German mathematician and philosopher who used a collection of pinwheels and stepped cylinders containing ridge-like teeth of different lengths corresponding to the digits 1 through 9. Baldwin replaced Leibniz's cylinders with a single cylinder with a variable number of teeth (1 through 9) protruding according to the motion of the setting lever. This evolved into the machines you see here which use a stylus to turn the wheels like a telephone dial.

Donor: Jim & Marie Petroff