Commonwealth 581 Admiration Professional Simplex Slide Rule

The Commonwealth Plastics Corporation of Leominster, Mass., a manufacturer of plastic toys, dolls, and other goods, made this one-sided, six-inch inexpensive white molded plastic slide rule with a clear plastic frameless indicator. The base has A and D scales, with B, CI, and C scales on the slide. The slide also has linear scales along its edges, inches divided to sixteenths of an inch and centimeters divided to millimeters. The back of the rule has a table of equivalents and abbreviations. The back is marked in script: Admiration. It is also marked: U.S.A. The rule fits into two slots in a yellow card. The front of the paper holder is marked: Instructions for use (/) on back of card; Admiration (/) PROFESSIONAL SLIDE RULE; EASY TO USE (/) No. 581. The back of the card gives directions and examples for reading the scales, locating the decimal point, multiplication, division, squares, square roots, and cubes. The card and rule are in a plastic bag stamped: 30¢.

Commonwealth Plastics was founded around 1923 and remained in business at 98 Adams Street until at least 1960. It was not a major manufacturer of slide rules.

References: "William Morris Lester (1908–2005)," The Plastics Collection, Syracuse University Library Special Collections Research Center, http://scrc.syr.edu:8080/content/lester_wm.php; Karen Nugent, "A City in the Making, from Pianos to Plastics: Industrial Past Spotlighted for Tour," Telegram & Gazette, Worcester, Mass., May 27, 2010; ad for Extrusion Supervisor, The Telegraph, Nashua, N.H., February 12, 1960, 10.

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