A fine English circular "twelve-ten" or "12-10" pocket calculator with leather case by Fowler & Co. in Manchester. Includes original instruction manual.

A form of a slide rule, it was designed for architects, builders, surveyors and timber merchants who often had calculations to make with decimal and duodecimal (12ths) notation. The calculator consists of two dials and two rotating knobs. The left hand knob rotates the dial and the right hand one rotates the cursor. There are 7 scales for converting twelfths to/from tenths, meters to yards, kg to lbs, inch to cm, tan and sine.

Fowler Calculators Ltd was a manufacturer of slide rules and other scientific and mathematical instruments, based in Manchester, England and founded in 1898 by William Henry Fowler. He was joined by his son Harold in 1905. The Twelve-Ten was introduced in 1936.

A great gift for an engineer, surveyor, or builder - or anyone collecting scientific instruments.