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    Gunnery callipers, French, 17th century.

    Callipers, used for artillery purposes, French, 17th century. Callipers were used to measure the diameter of cannon balls and the bores of cannons. This example also containd scales for artillery calculations

    GEM calculator, 1890.

    Gem' calculating machine, J.Guthrie's patent No 15062, 1890. The GEM calculator is a simple device for the addition of English money. Numbers are added by inserting a stylus against the figure and pulling downward.

    Rectangular protractor, late 18th century.

    Rectangular protractor in brass, engraved "Dollond, London", late 18th century.As well as the usual angular scale the instrument contains a diagonal scale for plotting distances on a map or plan.

    A sectioned Sinclair Executive pocket calculator, 1972.

    The Sinclair Executive Electronic Pocket Calculator (cutaway for exhibition) was the first electronic pocket calculator that could really fit into a pocket. Clive Sinclair (b. 1940) was able to achieve this by reducing the power input demanded by the

    Elka 101, electronic pocket calculator, 1976.

    Electronic Pocket Calculator by Isot, model Elka 101, c1976. Before the fall of the Iron Curtain in 1989, Bulgaria hasd one of the largest electronics industries in Eastern Europe. However in the 1970s they had to import the integrated circuits to co

    Surveyor's sector, early 17th century.

    Surveyor's sector, Italian, early 17th century, engraved "Adam Heroldt fecit Romae". The sector was invented independantly by Galileo and Thomas Hook at the end of the 16th century. It primarily measures proportions and can contain lines concerning t

    Napier's rods, 1671-1700.

    Napier's bones, cylindrical type, late 17th century. John Napier (1550-1617), discoverer of logarithms, created the popular calculating tool known as Napier's rods or bones. Napier's rods reduced muliplication to a sequence of simple additions; divis

    Model of a cylindroid, 1895-1900.

    Wire model of a 'cylindroid' by Howard Grubb, Dublin in brass glazed cylindrical case on a wooden base. The model was made on the instructions of Robert Stawell Ball who wrote the definitive work 'A treatise on the Theory of Screws' in 1900. Thomas G

    'Playskool' wooden toy, 1960-1980.

    Playskool wooden toy, a wooden framework with rotating blocks bearing numbers and symbols to do arithmetic. 1960-1980. Toys to help with arithmetic were introduced from the start of the 20th century.

    The 'Tell Bell' educational game, English, 1928-1932.

    The 'Tell Bell' educational game, made by Knapp Electrical Inc, a division of P. R. Mallory & Co. Inc.. An educational toy requiring the player to answer multiply choice questions involving mathematics. Answers are selected with template cards and