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Keuffel & Esser 68-1555 Doric Duplex Slide Rule

Keuffel & Esser 68-1555 Doric Duplex Slide Rule

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Usage conditions apply
This turquoise plastic 5-inch duplex slide rule has DF, D, and L scales on the front of the base and CF, CI, and C scales on the slide. The top of the base is marked: PAT. PEND.; CELANESE CELCON; MADE IN U.S.A. The right end of the slide is marked: DORIC (/) K & E CO. On the back, the base has K, A, D, and T scales, and the slide has B, ST, and S scales. The indicator is plastic, and the endpieces are metal.
The rule fits in a black leather sheath, embossed with the K+E logo and imprinted in gold: CELANESE CELCON (/) DESIGNED FOR THE ENGINEER ∙ ENGINEERED FOR THE DESIGNER. The sheath and a leaflet, "How to Take Care of Your Slide Rule," fit in a cardboard box covered with green vinyl. The end of the box bears a label marked: K+E (/) 68 1555 (/) POCKET SLIDE RULE (/) LEATHER SHEATH (/) MADE IN U.S.A.; TRADE MARKS ®. It is also marked there: OLD (/) 4168.
According to the donor, “The Celcon rule is significant because this is the first use of this very durable engineering plastic or resin in a slide rule. This durable material, trademarked Celcon, was an American invention made in the laboratories of the Celanese Corporation.” The donor was corporate research director at Celanese Corporation before he retired in December 1981. The 1962 Keuffel & Esser Catalog lists a 5" slide rule with model number 68 1555 made of “Ivorite.” The instrument is shown in the 1964 and 1967 catalogs (still as made of “Ivorite”) and called the “Doric.” It is not shown in the 1972 catalog. Celanese Corporation first used the term “Celcon” to refer to a thermoplastic in 1945, and trademarked the term in 1960. It seems likely that this rule was produced especially for Celanese Corporation in the period 1962–1971. This was the only time K&E manufactured a slide rule that was not white.
References: Joseph L. Soper, "The Celanese Celcon Promotional Slide Rule," in K&E Salisbury Products Division Slide Rules (Pleasanton, Calif.: The Oughtred Society, 2007), 115; Clark McCoy, ed., "K&E Catalogs and Price Lists for Slide Rules,"
Currently not on view
Object Name
slide rule
date made
Keuffel & Esser Co.
place made
United States: New York, New York City
Physical Description
plastic (overall material)
leather (case material)
paper (case material)
overall: 3.7 cm x 21.4 cm x 7.8 cm; 1 15/32 in x 8 7/16 in x 3 1/16 in
ID Number
accession number
catalog number
Credit Line
Gift of Alfred E. Brown
Rule, Calculating
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Slide Rules
Data Source
National Museum of American History
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