Adding Machine Model

This model of a nine-key non-printing adding machine has a wooden base, plastic sides, and a metal mechanism and keys. A bar across the back is moved in differing amounts according to the key pressed (the nine keys across the front are depressed in slots of varying length and hence rotate the bar varying amounts). The bar, in turn, rotates a numeral wheel with the numbers 0 to 99 on it. There is a one-digit carry. Keys are marked with the digits from 1 to 9 (the 5 key is missing). There is no 0 key.

The arrangement of the result wheels is somewhat similar to that on the ten-key machine invented by Peter Lindholm and patented in 1886. However, the number of keys and arrangement of the keyboard is different. The plastic sides also mitigate against a 19th century origin. No patent model was made for this patent, although there were production models.

Reference:

Peter Lindholm, “Adding Machine,” U.S. Patent 343770, June 14, 1886.

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