Underwood Sundstrand 10140P  
Written by Accutron on 2017-03-07  

The Undersood Sundstrand 10140P is one of many similar variants of the original ten-key adding machine invented by David Sundstrand in 1911. The Sundstrand adding machine is noteworthy as the first calculator to use a conventional ten-key entry method. Prior to the Sundstrand, all contemporary adding machines used a Comptometer-style full keyboard, with a nine-key column for each digit. A full keyboard is much faster for entry, as an entire number of any digit length can be entered in a single two-handed stroke. The ten-key keypad is much more user-friendly however, as it can be operated with a single hand, and does not require special training to use effectively.

In 1927, Sundstrand sold marketing and distribution rights of their machines to Underwood-Elliot Fisher Co, a leading typewriter manufacturer. Machines manufactured from 1927 onward bear the Underwood Sundstrand label. Oscar Sundstrand, David's brother and co-founder of the Sundstrand Machine Tool Co., joined Underwood after David's death in 1930, and continued to develop the Sundstrand adding machine until 1949.

The 10140P is a later motorized variant, with correction and repeat addition functions.

Underwood Sundstrand 10140P motorized 10-key adding machine.

This article is part of the [Mechanical Calculators] exhibit.

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