Keuffel & Esser 4081-3 Log Log Duplex Decitrig Braille Slide Rule

Some engineers continued to use slide rules even when they lost their sight. This is such an instrument; it may have been adapted from Keuffel & Esser's original product by the American Foundation for the Blind. The ten-inch duplex rule is made from mahogany coated with white celluloid and held together with metal end pieces. It has an oversized plastic indicator with plastic edges and is held together with plastic dowels. Instead of a hairline there is a piece of wire held taut between 2 plastic pegs on the open frame of the indicator. One side of the base has LL02, LL03 and DF scales at the top and D, LL3, and LL2 scales at the bottom. The other side has LL01, L, K, A, D, DI, and LL1 scales. The slide has CF, CIF, CI, and C scales on one side and B, T, SRT, and S scales on the other. Some divisions on the A scale and both D scales on the base and the T, S, and C scales on the slide are marked with raised metal dots. Some of these dots indicate numbers in Braille.
On one side, the right end of the slide is marked in red: © (/) K + E. On the other side, the left end of the slide is marked with a serial number: 397208. The left end of the top and the bottom of the base are both marked: 208. The top edge of the rule is marked: PATS. PEND. MADE IN U.S.A. 4081-3 LOG LOG DUPLEX DECITRIG ® COPYRIGHT 1947 BY KEUFFEL & ESSER CO. PATS. 2,500,460 2,168,056 2,170,144 2,285,722 2,422,649. Keuffel & Esser used this arrangement of scales on model 4081-3 from 1955 to 1962; the serial number suggests this example was made around 1958. See MA*318482 and 1990.0687.01 for nonadapted examples of model 4081-3. The instrument is in a very dark green leather sleeve fitted to the oversized indicator.
This slide rule belonged to Moritz Otto Shollmier (1931–1972), the late husband of the donor. He was a mechanical engineer who graduated from the School of Engineering at the University of Arkansas in 1956. He lost his sight in 1961 as a result of the effects of diabetes and used this instrument for several years to design heating and air conditioning projects. He was also an avid ham radio operator.
References: Ed Chamberlain, "Estimating K&E Slide Rule Dates," 27 December 2000,; accession file; Gordon Anthony, "The K&E Braille Slide Rule," Journal of the Oughtred Society 2, no. 1 (1993): 19–20; "Keuffel & Esser Braille Slide Rule," 2006.011.001, MIT Museum, ; "In Memory of WA5EFL Moritz Shollmier," (accessed October 24, 2001).
Currently not on view
Object Name
slide rule
date made
Keuffel & Esser Co.
Physical Description
wood (overall material)
celluloid (laminate material)
metal (part material)
leather (case material)
plastic (cursor material)
overall: 2 cm x 33.8 cm x 10.2 cm; 25/32 in x 13 5/16 in x 4 1/32 in
place made
United States: New York, New York
ID Number
catalog number
accession number
Rule, Calculating
Science & Mathematics
Slide Rules
See more items in
Medicine and Science: Mathematics
Slide Rules
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Liane Humble
Additional Media

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