Keuffel and Esser’s “‘Duplex’ Slide Rule” Advertisement
This advertisement for a Cox model duplex slide rule explained the new features of the rule, described how it worked, and noted how it differed from the Mannheim style rule.
Advertisement for Keuffel and Esser’s “‘Duplex’ Slide Rule,” Scientific American, vol. LXIX, no. 7, (August 12, 1893), p. 101. This advertisement for a Cox model duplex slide rule explained the new features of the rule, described how it worked, and noted how it differed from the Mannheim style rule.
