CHM Revolution

Date Introduced

1969

Photographer

Richards, Mark

Dimensions

overall: 1.25 x 7.5 x 1 1/4 in.

Manufacturer

Otis King

Credit Line

Courtesy Gwen and Gordon Bell

Copyright Owner

© Mark Richards

Location

United Kingdom

Keywords

Oughtred, William; Analog; Hand calculation

Object ID

B311.84

Cost

$10-25

This 60-inch rule could be closed and slipped in a pocket. The “Model K” had just two scales and could only multiply and divide.