Scientific Instruments > Calculating

Halden Calculex Circular Slide Rule circa 1910

Item#: SCI1236

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Halden Calculex Circular Slide Rule circa 1910 - click to enlarge.

This is a circular side rule made of German silver and glass by the J. Halden Co. Ltd. of Manchester. It comes with a booklet of instructions which tells us that: 'It cosists of a disc within a ring which together form a dial with logarithmic scales... ' Halden produced the calculex slide rule from about 1910 to 1951 The Calculex is unique in not using a knob winder; instead the nut in the middle is rotated . This is one of the earlier versions of the calculex probably made in 1910 or early 1911. Comes in its original leather case marked with the retailer's name -Eugen Dietzgen Co.