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    Chuckrum board, Indian, late 19th century.

    Chuckrum board with 108 small coins.This board was used to count 100 small 'chuckrum' coins rapidly by spreading them over the surface to fill the holes.

    Kelvin's harmonic analyser, 1878.

    Kelvin's harmonic analyser, 1878. The machine was Invented by William Thomson, Lord Kelvin, (1824-1907), a pioneering Irish physicist. The harmonic analyser was designed to analyse graphical records of daily changes in atmospheric temperature and pre

    Arithmetical Jewel, 1619.

    The 'Arithmetical Jewel' publicised by William Pratt in 1619. This instrument combines features of an abacus with those of pen reckoning. Numbers are put in by moving the flags to reveal dots. Sums are then worked out with a pen and paper.

    Exchequer tally and foil, English, 1822.

    An exchequer tally dated 1822. The English Exchequer used tallies to record deposits from the mid-12th century until 1826. Notches show the amount paid; differently spaced notches standing for a penny, a shilling, £1, £20, £100 and £1000.

    Boxwood Coggeshall folding slide rule, 1720-1730.

    Boxwood Coggeshall rule, folding with slide, c. 1720-1730. Until the early 19th century slide rules were usually made for specific trades. This is a type of carpenter's rule.

    Klein bottles, 1995..

    A single surface glass vessel made by Alan Bennett in Bedford, United Kingdom. It consists of three Klein bottles sharing an inlet tube which when cut produces three pairs of single-twist Mobius strips. A Klein bottle is a surface which has no edges,

    Klein bottle, 1995.

    A single surface model made by Alan Bennett in Bedford, 1995. It consists of a Klein bottle cut to form two interlinked three-twist Mobius strips. A Klein bottle is a surface which has no edges, no outside or inside and cannot be properly constructed

    Coradi planimeter and map, 1886.

    Planimeter (rolling type) by G. Coradi, Zurich, in case, 1886. Planimeters were used by engineers and scientists to measure the area inside a closed curve.

    Bissaker's slide rule, 1654, and Thacher's calculating instrument, 1881.

    The earliest known dated slide rule, made by Robert Bissaker, which uses scales bound together with metal bands.

    Henrici's harmonic analyser, No 3, 1894.

    Harmonic analyser designed by O.Henrici, made by G. Coradi, 1894. Harmonic analysers were designed to break down a complex wave, such as a sound wave, into its fundamental and harmonic components. This one uses the motions of three glass spheres whic