Rear Scales

Scales are listed in order from top to bottom.

Keying of S Scales
Mannheim slide rules have S, L, and T (sine, logarithm, and tangent) scales on the back of the slide.  The S scale is angles (marked in degrees) and the sines of those angles are read from the "B" scale on the face of the slide.  For example, the sine of 20^o is 0.342 and that number appears on the B scale exactly opposite 20^o on the S scales.  The S scale runs from 0^o 34' to 90^o and the B scale runs from  0.01 through 0.10 to 1.0.  This is the standard arrangement of the S scale on "Mannheim" slide rules. The Hemmi Catalogue Raisonne assumes that where the scales are listed as S, L, T, the S scale is keyed to the B scale.               

Rietz slide rules have S, S&T, and T (sine, sine & tangent,  and tangent) scales on the back of the slide.  The S scale is in degrees, as with Mannheim rules, but the sines of those angles are read from the "C" scale on the front of the of the slide.  The sine of 20^o (0.342) is on the "C" scale, opposite 20^o on the S scale.  This the standard arrangement of the S scale on "Rietz" slide rules.  The Hemmi Catalogue Raisonne assumes that where the scales are listed as S, S&T, T, the S scale is keyed to the "C" scale.  

Between about WWII and 1955 Hemmi experimented with Rietz scales on their Mannheim rules.  Such rules are indicated by "S keyed to C/D" in the Hemmi Catalogue Raisonne.  (The Frederick Post and Hughes -Owens companies in North America resisted this experiment and few, if any, of the Mannheim rules they distributed have the S scale keyed to C/D.)  Hemmi abandoned the experiment about 1955 and went back to the traditional keying of the S scale.