Single surface models made by Alan Bennett in Bedford, 1995. Three toroid single surface vessels, one with the loop inside the torus, one with a narrow loop outside and one with a wider loop outside. All can be cut to produce a pair of single-twist M
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
S & N adding machine by Seidel & Naumann, Dresden, serial no. 2398, in fitted box with stylus and instructions. The Seidel and Naumann adding machines used chain drives and a stylus. The numbers to be added were pulled down to the base bar and then a
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.
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,
A single surface glass vessel made by Alan Bennett in Bedford, 1995. Its form is a variation on the Klein bottle with an inlet passing through the vessel which when cut forms a pair of single-twist Mobius strips. A Klein bottle is a surface which has
Set of 'arithmetical scales' by Smith and Dolier, late 19th century. These 'scales' were used to set many different sums in addition and subtraction. Pupils in a class would probably have used slates to do the sums.
Mechanical counting device, c 1900. Devices for counting the revolutions or repetitive actions of machines were developed from the mid 19th century.
`Baby Calculator' stylus adding device by Glenview, Illinois, USA, c. 1960. Like the Exactus, this is one of a number of simple stylus machines introduced in the mid 20th century. It performs multiplication and division by repeated addition and subtr
Elliptic trammel by Stanley, 1876. Trammels were used for curve drawing from the Rennaissance until the use of computers made them obsolete.