Marchant Calculating Machine, circa 1935

Mechanical adding machines were indispensable--and almost indestructible--office equipment used before the computer era. Marchant was the first American firm to specialize in calculators, which could perform at least the basic mathematical functions of addition, subtraction, multiplication and division; an improvement over two-function adding machines. Founded in 1911, Marchant was absorbed by Smith-Corona Co. in 1958.