Sundstrand Adding Machine - Underwood 10 Key

Sundstrand Adding Machine - Underwood Sundstrand

Sunstrand Adding Machine - Underwood Sunstrand 10 key Listing Machine

The Sundstrand Adding Machine circa 1920
Rockford, Illinois U.S.A source: ebay and various (including PierceFuller)

David Sundstrand, in 1911, invented an adding machine that was the very first to use the '3x3 above zero' key arrangement, which became widely adopted and to this day is standard on calculator and computer keypads around the world.

Sundstrand 10 key keypad closeup circa 1914

The Sundstrand was the first to use this 10-key arrangement, which is ubiquitous today.

The red keys are: 'Non-Print', 'Error', 'Repeat', 'Lock', 'Non-Add', 'Total'.

Sunstrand Adding Machine - Underwood Sunstrand 10 key Listing Machine with direct subtraction Saturday Evening Post

Ads for The Sundstrand Adding Machine 1923

This machine was the first in the U.S. to offer 'Direct Subtraction'

Saturday Evening Post (source: AdsOfThePast with permission)

The Otis King Patent Calculator with cursor in brass

David and Oscar Sundstrand

In 1927, Oscar (the younger brother) and David Sundstrand sold the rights to market and distribute the Sundstrand machine to Underwood-Elliot Fisher Co., a typewriter and office equipment manufacturer, and the machines thereafter bore the mark of Underwood Sundstrand. David died in 1930, but Oscar joined Underwood and continued developing the Sundstrand adding machine until 1949. He later joined Victor and helped design their successful line of printing calculators in the 1950s.