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Sperry's Calculator
c. 1900
Model 4016, Serial #51

Patented on Oct. 25, 1904, this rare version of a circular slide rule was the creation of Elmer Ambrose Sperry, a prolific inventor with over 350 patents and whose name was later associated with Sperry-Rand. His circular calculator was first sold by Keuffle and Esser (K&E) for $20 in their 1906 catalog. Made to resemble a pocket watch, they did not sell, probably due to their cost, which was about four times as much as a 10-inch wooden slide rule.

Donor: Jack W. Flinn


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2006 San Diego Computer Museum
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