Pins and Levers

Frank Baldwin’s 1872 “pinwheel” calculator design was the first significant advance since the 1820 Thomas Arithmometer. Zero to nine teeth protruded from a thin “pinwheel” gear, depending on the position of a lever set by the operator. The number of protruding pins determined the digit entered by turning the gear. Additional gears in a row allowed multi-digit numbers. Other manufacturers copied Baldwin and eclipsed his tiny production.