Wanted: Patent Revolving Interest Calculator
During the 1st half of the 19th century, inventors like Joseph Jelleff and Gilbert Lowe took out patents for devices with 2 overlapping paper discs on a single pivot point with tables to automatically calculate interest. Know examples of such devices were printed by Wright & Legg of Columbus, Ohio, C.M. Riley of Cincinnati, Ohio and T.C. Strong for L. Walker & Co. of Middelbury, Vermont.
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