Type: Mechanical Calculator
Size: 12"W x 10"D x 7"H / 30 cm W x 25 cm D x 18 cm H
Serial Number: 13-38366
The pinwheel calculator was invented in the late 19th century and was the standard desktop unit in financial offices until the 1960s. The "pinwheels" were the drums at the heart of the calculator. The drums were set by little tabs and then rotated by a large crank to add and subtract to an accumulator. A third register counted the number of times you cranked the crank and the accumulator could be shifted to the left and right. These features allowed for quick multiplication and division.
The 13RK included a "register transfer" feature that moved the value in the accumulator into the input register, setting the drums for the next calculation.