Safe-T 45749 Compass

This translucent light orange plastic instrument is wedge-shaped, with a rotating white plastic disc set inside the wide end of the wedge. One long edge of the wedge has a scale of four inches, divided to 16ths of an inch. The other edge has a scale of ten centimeters, divided to millimeters. These edges each have a row of 33 small circular holes. The holes are marked for the radius of various circles, from 1" to 5". To draw a large circle, a pencil is placed in the desired hole and the instrument is rotated while the user holds the disc.

Two rows of four small holes are on the disc; one row is straight and one is bowed. The disc also has a small hole at its center. To draw a small circle of up to 1-5/8" diameter, a pencil is placed in the desired hole and used to rotate the disc, while the wedge is held in place. Five larger circles are around the edge of the disc. The wedge is marked: SAFE-T (/) COMPASS® (/) LaGrange, IL 60535-0692 (/) #45761 Pat. #4,353,166. It is also marked: π = 3.1416 (/) A = πr² (/) C = πd.

Instructions are on white cardboard received with the instrument. According to a company catalog (1998.0033.04), model number 45759 sold for $1.19 around 1998. The design of the disc is covered by a patent received by John S. Kettlestrings of Wheaton, Ill., in 1982.

Safe-T Products, Inc., of La Grange, Ill., was established in 1992 and specialized in drawing instruments that were safe for children. In 2006, the company became a subsidiary of A. Daigger & Company and its name changed to Classroom Products Warehouse. Kettlestrings (b. about 1933) is an inventor, designer, and entrepreneur who was associated with Tool-Less Hanger Corporation of Everson, Wash., in 2011.

References: SAFE-T Products, Inc., Innovative Safe Drawing and Measuring Instruments, about 1998; John S. Kettlestrings, "Toy-Like Instrument for Drawing Circles" (U.S. Patent 4,353,166 issued October 12, 1982); Company Overview of Safe-T Classroom Products, Inc.," Bloomberg BusinessWeek, http://investing.businessweek.com/research/stocks/private/snapshot.asp?privcapId=27794340; "About Us," Classroom Products Warehouse, http://www.classroomprdcts.com/.

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