C-Thru Pocket Slide Rule

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This inexpensive five-inch white plastic rule has A and D scales on the front of the base; B, CI, and C scales on the front of the slide; and S, L, and T scales on the back of the base. The indicator is clear plastic. Underneath the slide is a table of equivalents and settings. The front of the slide also has a scale of six inches, divided to sixteenths of an inch, and a scale of 15.3 centimeters, divided to millimeters. The back of the slide has a table of decimal equivalents from 1/64 to 63/64. A brown imitation leather sheath is marked: POCKET SLIDE RULE MADE IN U.S.A. No. 27. For instructions, see 1988.0807.06. The postal code on the instructions indicates a date between 1943 and 1963. According to this sheet, the C-Thru Ruler Company of Hartford, Conn., made this rule. This firm, established in 1939 by teacher Jennie Zachs and acquired by Acme United Corporation in 2012, continues to make transparent drafting tools and drawing instruments.
References: Brian Dowling, "Acme United Acquires Bloomfield's C-Thru Ruler," Hartford Courant, June 11, 2012; "About Us," C-Thru Ruler Company, http://www.cthruruler.com/.
Currently not on view
date made
C-Thru Ruler Company
place made
United States: Connecticut, Hartford
Physical Description
plastic (overall material)
overall: .4 cm x 17 cm x 4.4 cm; 5/32 in x 6 11/16 in x 1 23/32 in
ID Number
accession number
catalog number
Credit Line
Gift of George A. Norton
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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