Circular slide rule by Troughton and Simms, designed by William Froude c.1877, with inscription plate and three logarithmic scales, used at the Admiralty Experimental Establishment, by Troughton and Simms, London, 1887 Circular slide rule Froude 1877

Boots Ring Plan Standard 5-inch slide rule with plastic sleeve and instructions Boots Ring Plan Standard 5-inch slide rule with pl Mathematics 1970-1980

Slide rule for triangle-mesh-reinforced concrete slabs, celluloid, copyright 1909 by the American Steel and Wire Company Slide rule for triangle-mesh-reinforced concrete s Mathematics 1909-1915