Schickard's concept was brilliant. He used a set of revolving cylindrical Napier Bones, for multiplication. Addition was performed by turning the dials on the lower part of the machine. These dials were connected with internal wheels, with teeth on their circumference, causing a carry as the wheel passed from 9 to 0. Subtraction was preformed by reversing the wheel.

This model was built by IBM Germany, based on the few available drawings, and is in our collection.

It was another 25 years before the first digital calculating machine materialized.