Friedmann Mannheim
This rare model, was fabricated in Germany apparently by Faber-Castell for a distributor in the USA: Friedmann Bros, a company dedicated to commercialize drafting tools during the 1930's. This assumption may be supported because the table on the back face is written in English.
It was fabricate with wood (Mahoganny?) covered with celluloid strips riveted to the wood, but glued on the slider, where scales were engraved. The cursor was all crystal glued to metallic ends, and it has three lines: the conventional central hairline and two additional gauge lines.
I have not found more information about this model other than auctions records. Only the International Slide Rule Museum has a model like this in its German Rules collection identified as Friedmann Mannheim.
The 10 inches long scales on this 12 inches long rule are: 11 inches - A [ B, CI, C ] D, K - 11 inches on the front face, and [ S, L, T ] on the slider's back. These trigonometric scales are divided in degrees-minutes. Notice that the scales on the front face are not labeled. On the rule's back face there is a very dense table with unit conversions, equivalences, and materials specific weights which makes that think this rule was produced to be used in the engineering field, possibly chemistry.
This model, as other German rules fabricated before 1955,do not have printed or engraved serial numbers, and the difficulty to find product catalogs do not let determine fabrication years with precision.
The next operations can be performed with a precision two or three decimals with any of these rules:
SRPractice-1.pdfI have not found manual for this rule made by Friedmann Bros, but it can be used others' Mannheim slide rules manuals, like the K&E 4053.
