Nestler 23R Simplex Slide Rule

This one-sided, ten-inch wooden slide rule has lengths of white celluloid screwed to all sides except the back. The indicator is glass with metal edges. The top edge of the base has a scale of 28 cm, divided to millimeters. The scales on the base and one side of the slide are not labeled. The top of the base has a scale divided logarithmically from 1 to 1,000 (i.e., from 1 to 10 three times) and a scale divided logarithmically from 1 to 100 (1 to 10 twice), which is repeated on the front of the slide. These are equivalent to K, A, and B scales. The second scale on the slide is divided logarithmically from 10 to 1. The third scale on the slide and the first scale on the bottom of the base are divided logarithmically from 1 to 10. These are equivalent to CI, C, and D scales. The bottom scale on the base is divided from 0.1 to 1.0 in equal parts (i.e., an L scale).

The scales on the back of the slide are lettered S, S&T, and T. Underneath the slide is a centimeter scale, marked from 30 to 56 and divided to millimeters. The instrument is marked there: Tailhade & Cia., Cangallo 445 Bs. - Aires SYSTEM REITZ N^o 23 R ALBERT NESTLER A.-G. LAHR i/B. D.R.G.M. D.R.PATENT Industria Alemana. The front of the instrument has a scale of equal parts labeled 1:25. Tables of constants and material properties, in Spanish, are on paper pasted to the back of the instrument. A cardboard box covered with black synthetic leather is marked: Albert Nestler A.G. (/) D.R.Patent Rietz N^o 23 RF (/) Industria Alemana. The box is also marked TAILHADE & Cia. (/) CANGALLO 445 (/) Bs. Aires.

The German firm of Albert Nestler established a factory in Lahr in 1878. (The "i/B" marked on the rule stands for "in Baden.") In 1902 Nestler began to offer slide rules with the arrangement of scales proposed that year by German engineer Max Rietz. These included the K and L scales, with the CI and ST (called S&T on this example) scales added about two decades later. The company held numerous German patents. Nestler first advertised model 23 with Rietz scales in 1907. The donor purchased this rule at a bookstore in Argentina around 1940, which is about the same time that Nestler stopped attaching celluloid to rules with screws.

Reference: Guus Craenen, "Albert Nestler: Innovation and Quality," Journal of the Oughtred Society 11, no. 1 (2002): 38–46; Dieter von Jezierski, Slide Rules: A Journey Through Three Centuries, trans. Rodger Shepherd (Mendham, N.J.: Astragal Press, 2000), 34, 64–68, 118; Peter M. Hopp, Slide Rules: Their History, Models, and Makers (Mendham, N.J.: Astragal Press, 1999), 96, 98.

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