Fowler Vest Pocket Calculator

Fowler's Vest Pocket calculator with cloth cover, case and instruction leaflet, 1950-1955.

"The Fowler Calculator is a type of circular slide rule, a sort of mechanical calculating device, popular in the time before electronic calculators were developed.

Slide rules have a number of different moveable scales on them. By moving the scales on the slide rule, counting the number moved, and comparing the results between them, it is possible to do a range of calculations quite quickly, particularly multiplications, divisions, and conversions between different units. Many slide rules are shaped like straight rulers, but this one is pocket-watch shaped, with the scales adjusted by twisting the knobs on the edge.

It was made by Fowler & Co, a Manchester based company, originally established as the Scientific Publishing Company in 1898 by William Henry Fowler. The firm began offering pocket-watch calculators in 1898 and manufactured devices of this type for several decades, with William Fowler and his son Harold patenting several improvements. The firm offered a whole range of calculators, some intended for general use and others manufactured for the calculations common in specific industries.

This particular Fowler's Vest Pocket calculator was made in the early 1950s and intended to do a range of calculations. Its small size made it easy for workers to carry around. "