Nestler Rietz No. 23RF

The System Reitz No. 23 slide rule was manufactured in Germany in the period 1907-1940, according with the information I found in the Website of the National Museum of American History for the Nestler 23. The lack of printed or engraved serial numbers on many Nestler models, as well as product catalogs are very difficult to find, make difficult to determine fabrication years with precision. The Rietz 20/1 model can be seen in the 1938 catalog.

The Rietz No.23R was fabricated with Mahogany covered with white celluloid screwed to the wood body in some models until about 1940. With glass indicator metallic holders. The scales on the Rietz No. 23 are Centimetres K, A [ B, CI, C ] D, L Inches on the front face, and [ S, ST, T ] on the slider's back. These trigonometric scales are divided in degrees-minutes. On the rule's back face there is a very dense table with unit conversions, equivalences, and materials properties, which makes that think this rule was created for the engineering field. According with the document Slide Rules of the Rocket Pioneers, The Nestler 23R was Werner Von Braun and Sergei Ko;rolev (Rocketry pioneer scientists ) favorite slide rule. In the same paper is stated that it was also Albert Einstein's preferred rule.

There were some variations in the Rietz No. 23 during the production years. The model in this collection has the top cubic triple logarithmic scale divided from 1 to 1,000 (i.e., 1 to 10 to 100 to 1000), and the quadratic double scales divided from 1 to 100 (1 to 10 to 100). Also the single and double logarithmic scales have extended scales at their ends. As many other Nestler rules, this model does not have labeled the front scales, only the scales on the slider's back are labeled.