This clear plastic sixth-circle protractor is divided along its outer edge by hundredths and marked by tenths from +1.7 to +0.1 (in black print) and from -0.1 to -3.4 (in red print). The scale is labeled: TIME INTERVAL, SECONDS. The left edge of the protractor is divided by tens and marked by hundreds from 2000 to 600. The scale is labeled: LENGTH OF SUB-BASE, YARDS. The right edge of the protractor is divided by halves and marked by ones from 14 to 1. The scale is labeled: THOUSANDS OF YARDS (/) 1/25000.
The interior of the protractor is filled with diagonal lines. Three scales are among the diagonal lines, each numbered by tenths in black and in red print. The outermost is numbered from 3.9 to 0.1; the middle scale is numbered from 3.0 to 0.1; and the innermost is numbered from 2.2 to 0.1.
The maker's mark is near the vertex, which is notched: 2 SOUND SECONDS (/) TEMPLATE, 1/25000 (/) FELSENTHAL INSTRUMENTS CO. (/) MFR'S PART NO. FAE-19B (/) MFR'S CODE 22040. There is a large plus sign to the right of the maker's mark.
The Chicago firm that manufactured this protractor was known as Felsenthal Instrument Co. in the 1960s and 1970s. Ben Wharton Rau (1904–1995) and his wife, Margery Felsenthal Rau (1916–2010), arranged the donation of this object and many other instruments to the Smithsonian. Margery's father, Irving (1887–1956), was one of the "Sons" of G. Felsenthal & Sons, as the company was known in the 1940s and 1950s. Margery's grandfather, Gabe Felsenthal, founded the firm in 1899.
Ben Rau worked for the Felsenthals. His duties included touring military facilities with a large display of the company's products. He catalogued hundreds of instruments when the company went out of business in 1976. He dated this protractor and 1977.1141.01 to 1950. While the form was indeed probably older, the maker's name on the instrument indicates it was manufactured in the 1960s or 1970s. Rau also held patents on a collapsible film reel, a proportional divider, and a belt buckle assembly.
See also 1977.1141.01, 1977.1141.03, 1977.1141.05, 1977.1141.08, 1977.1141.09, 1977.1141.10, 1977.1141.11, 1977.1141.12, 1977.1141.18, 1977.1141.19, 1977.1141.20, 1977.1141.21, 1977.1141.22, 1977.1141.23, 1977.1141.24, 1977.1141.30, and 1977.1141.39.
References: Deborah J. Warner, “Browse by Maker: Felsenthal,” National Museum of American History Physical Sciences Collection: Navigation, http://amhistory.si.edu/navigation/maker.cfm?makerid=173; "Irving G. Felsenthal," Chicago Tribune, February 26, 1956, http://www.susaneking.com/genealogy/showsource.php?sourceID=S01752&tree=GreenebaumSam; Copyright Office, Library of Congress, "Books and Pamphlets," Catalog of Copyright Entries, 3rd ser., 16, part 1, no. 2 (1964): 1392; Ben W. Rau, "Collapsible Film Reel" (U.S. Patent 3,447,759 issued June 3, 1969), "Proportional Divider" (U.S. Patent D214,399 issued June 10, 1969), "Belt Buckle Assembly" (U.S. Patent 3,475,797 issued November 4, 1969).
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