A single surface model made by Alan Bennett in Bedford, 1995. It consists of a sphere with three interlinked loops the equivalent of three interconnected Klein bottles. A Klein bottle has no edges, no outside or inside and cannot be properly construc
A single surface model made by Alan Bennett in Bedford, 1995. This 'way-in-way-out vessel' is equivalent to two Klein bottles, one inverted, sealed together back-to-back. When cut it forms two pairs of single twist Mobius strips. A Klein bottle is a
Exactus stylus-operated adding and subtracting device, with swivelling half plate for add and subtract options, marked "Mini-Add Made in England", c. 1950. The Exactus is one of several simple stylus-operated calculators to have been popular in the
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
Harding's improved counter by Harding, Richardson, Rhodes and Co. Ltd., Leeds. Revolution counters were devised to keep a record of the operation of machinery.
Numeric Demonstrator', an elementary teaching aid patented by Ethel Linay in about 1900.. This elementary arithmetical teaching apparatus consists of ten wooden rods with squared paper pasted on them in order to show multiplication visually.
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
Consul' the Educated Monkey. A mathematical toy calculator patented by William Robertson in 1916 and made by the Educational Novelty Company of Dayton, Ohio, USA. When each of the monkey's feet are moved to point at two numbers, the monkey's hands m
A single surface glass vessel made by Alan Bennett in Bedford, 1995. 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, no outsid
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