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S/5256 Antique Telescopic Otis King's Circular Pocket Calculator

An interesting telescopic pocket calculator, inscribed Otis King's Pocket Calculator Scale No. 430 Copyright London Patentees & Sole Manufacturers Carbic Ltd. The metal cylinder, covered with paper computations and sliding hand grip, has its original leather travelling case, all legible and in good condition throughout.

Otis Carter Formby King was an electrical engineer in London, who invented and produced a cylindrical slide rule with helical scales, primarily for business uses initially. The product was named Otis King's Patent Calculator and was manufactured and sold by Carbic Ltd. in London from about 1922 till 1972.

Length extended: 10.25 inches (26 cm.)

Sold 6 in. (15 cm.) Wide
1 in. (3 cm.) Diameter English Circa 1930