A. W. Faber Mannheim Simplex Slide Rule

This one-sided, ten-inch wooden rule has a layer of yellowed white celluloid on the front side. It has unlettered A and D scales on the base and B and C scales on one side of the slide. The other side of the slide has S, L, and T scales. The indicator is glass in a metal frame. The top edge is beveled and has a 25-centimeter scale, divided to millimeters. A second scale, 26 centimeters in length, is on the front edge. Underneath the slide is a third centimeter scale, numbered from 27 to 51.

The bottom of the base is marked in gold: A. W. FABER. Tables of equivalent measures and lists of constants (in German) are printed on paper glued to the back of the instrument. The rule is in a cardboard case covered with black leather, which is in excellent condition. The case is marked: Rechenstab (/) von (/) A. W. Faber. The back of the case is signed illegibly in pencil.

A. W. Faber began manufacturing wooden slide rules in 1882 and added celluloid facings in 1887. From about 1888 to 1900, the rules were often marked not only "A. W. FABER" but "Made in Germany." The metal indicator with a glass window was introduced in 1889. Although there is no model number on this rule, in the 1910s this combination of scales and indicator was sold as model 360. See MA.304722.02 for a later version of this rule, which mentions an 1899 patent and has a digit registering indicator introduced in 1905.

Reference: Dieter von Jezierski, Slide Rules: A Journey Through Three Centuries, trans. Rodger Shepherd (Mendham, N.J.: Astragal Press, 2000), 54, 90; Trevor Catlow, "Suggestions for Dating pre-1920 Faber Castell Slide Rules," Journal of the Oughtred Society 18, no. 2 (2009): 46–53; "Time Line for A. W. Faber and Faber-Castell," http://sliderulemuseum.com/SR_Dates.htm#Faber.

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