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This is a pencil-box calculator for primary school students aimed to memorize the multiplication table. It was invented and pa tented in England in 1921 and manufactured by Darnley's under the name ‘Rotatable Lightning Calculator, Pencil Case, Ruler & Measure’. It consists of two tin cylindrical drawer tubes that could be rotated to perform the calculation. The multiplication table is printed on the inner tube while the outer tube is perforated with windows to show the results. It carries a British patent number 167699/21 and a German patent No. 797458. Length: 235 mm, Diameter: 30 mm. It is said that, the study desk of the 1925 Nobel price winner George Bernard Shaw, is the essence of the man: His love for gadgets is revealed through oddities left on his desk. One such item a 'Darnley's Patent Rotatable Lightning Calculator, Pencil Case, Ruler and Measure'. |
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