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Twelve German jetons, 16th century.

Twelve replica German jetons, originals date from the 16th century. These small counters were placed on a counting cloth in a similar manner to beads on an abacus.

Felt and Tarrant Comptometer, 1887.

An early example of the Comptometer, with 72 numbered keys. The top of box has a plate engraved with varoius patents up to 1891. The Felt and Tarrant Comptometer was one of the first generation of mass-produced office calculators. It was extremely su

Brass sector, 1623.

Brass sector (Gunter's pattern) by Elias Allen 1623. Allen made the sector to the design of Edmund Gunter who published a description of it in the same year. Sectors were used from the end of the 16th century until the mid 19th for calculations invol

Gunner's quadrant and perpendicular, c 1780.

Gunner's quadrant and perpendicular by George Adams the Younger, c.1780. This instrument was designed primarily to ensure that a cannon or mortar was elevated to the required angle. Quadrants were also used for navigational purposes to determine the

Japanese abacus, c 1900.

Japanese soroban or abacus with 13 columns, each with 5 beads below the bar and one above.This represents an intermediate form between the original Chinese abacus and the modern Japanese type. This arrangement was common from the late 19th century u

GEM calculator converted for Indian currency, 1912.

Stylus-operated Indian currency adder, wooden backboard with handmade varnished card face inscribed 'R.G.W. 24.2.12'. The GEM calculator was originally patented in 1890 as a simple device for the addition of English money. Numbers are added by insert

McFarlane calculating cylinder, 19th century.

McFarlane calculating cylinder, c1835. This is a ready reckoner inscribed with tables giving various percentages of various sums of money in sterling.

The 'Tachypoly Plasiasme' ready reckoner, 1880-1884.

'Tachypoly Plasiasme' ready reckoner, 1880-1884. Invented by C L Chambon in 1880, the 'Tachypoly plasiasme' ready reckoner showed multiplication tables up to 100 times 100.

Cardboard models of Second Order Surfaces, 1901.

Set of 7 assembled cardboard geometrical models on wooden stands showing the surfaces of the second order.

Klein bottle, 1995.

A single surface model made in glass by Alan Bennett in Bedford, 1995. It consists of a Klein bottle with three loops, one of which has been cut away and sectioned to form a pair of single twist Mobius strips. A Klein bottle is a surface which has n