Charles Bruning 2401 Simplex Slide Rule

Charles Bruning 2401 Simplex Slide Rule

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This one-sided, five-inch white molded plastic linear slide rule has a glass indicator with a metal frame. The top edge is beveled and has a 12.5 cm scale, divided to millimeters. The top of the base has an A scale and is marked: CHARLES BRUNING CO. It is also marked: MADE IN U.S.A. The slide has B, CI, and C scales on one side and S, L, and T scales on the other side. The left end of the front of the slide is marked: 2401. The bottom edge of the rule is beveled and has a five-inch scale, divided to 32nds of an inch. Three screws on the back of the rule permit the top of the base to be adjusted.
The instrument fits in a brown leather sleeve, which in turn fits in a red cardboard box. The box is marked: BRUNING (/) [Bruning logo of CB inside a diamond] (/) CHARLES BRUNING COMPANY, INC. A slip of paper inside the box advertises a magnifier that could be ordered for 60 cents from any of fourteen Bruning branch offices located across the United States. For an instruction manual received with the instrument, see 1991.0445.03.01.
Charles Bruning (1866–1931) was born in Denmark and immigrated to the United States. In Chicago during the 1890s, he became interested in the blueprint business. In 1897 he set up his own blueprinting company in Manhattan, which was incorporated at the New York Blue Print Paper Company in 1901. Around 1920 he purchased American Blue Print Company of Chicago, and the combined firms became known as the Charles Bruning Company, Inc. The company's 1921 catalog lists eleven slide rules, although it is unclear whether any of these were actually manufactured by Bruning. By 1936 a new system of numbering was introduced. It assigned different model numbers to slide rules sold with different types of cases. This increased the number of model numbers to 14, but only 8 of these appear to be distinct. By 1952 most slide rules sold by Bruning were all-metal slide rules manufactured by Pickett & Eckel. This all-plastic rule is an exception.
The instruction manual was copyrighted in 1944. This model is not shown in the 1939 Bruning catalog. By 1952 the indicator was of a different form. Hence, this rule likely dates from 1944 to 1951. The Charles Bruning Company merged with the Addressograph-Multigraph Corporation in 1963.
References: New York Blue Print Paper Company, Catalog (New York, 1921), 155–157; "Charles Bruning," New York Times (January 31, 1931), 14; Charles Bruning Company, Inc., General Catalog (New York, 1936), 130–134; Charles Bruning Company, Inc., General Catalog (New York, 1939), 146–152; Charles Bruning Company, Inc., General Catalog (Teterboro, N.J. and Chicago, 1952), 121.
Currently not on view
Object Name
slide rule
date made
Charles Bruning Company
place made
United States: New York, New York City
Physical Description
plastic (overall material)
glass (cursor material)
metal (part material)
leather (case material)
paper (case material)
overall: 1.6 cm x 17.8 cm x 5.5 cm; 5/8 in x 7 in x 2 5/32 in
ID Number
accession number
catalog number
Credit Line
Gift of Richard R. Lombardi
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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"I recently received a Bruning Slide Rule Md#2401 in a hard black case. all of my machining tools are from 1936 to 1944 so i was wondering if this may be one of the ones manufactured from the original catalog. The slide rule itself does not have any of the company information on it. It is an all plastic ruler, It has a paper instruction manual. on the bottom of the manual it says Indicator Patent Applied for. Thank you. Ron Cuellar "

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