Safe-T 45700 Bullseye Compass

Like 2000.0160.06, this red and white plastic instrument combines a ruler, a protractor, and a compass. Unlike 2000.0160.06, this object is smaller, white instead of clear, and uses a slide instead of rows of holes for setting the radius of a circle. The semicircular (protractor) end is wider than the rectangular part of the instrument. It is marked in 15-degree increments in both directions, from 15 to 165 degrees, and divided to units of five degrees.

Inside the arc is a small rotating disc. The rectangular ruler has a groove down its center that carries a sliding red plastic piece with two holes in it. This piece can be set anywhere along the scales on the ruler, giving the distance from the center of the small disc. Placing a writing implement in one of the holes and rotating the ruler while keeping the disc fixed gives a circle of the radius set. One of the long edges has a ruler 12 centimeters long, divided to millimeters. The other edge has a five-inch ruler, divided to 16ths of an inch.

The back of the instrument is marked: U.S.Pat. # 5,615,485 (/) Other Pats. Pend. The back of the slide is marked: MADE (/) IN CHINA. The Bullseye Compass was introduced in 2000 and retailed for $1.99 in 2012.

References: Learning Resources online catalog (accessed October 22, 2012); Ho Chan, "Adjustable Compass with Ruler and Protractor" (U.S. Design Patent 411,959 issued July 13, 1999); J. Bruce Stoneberg, "Drawing Tool" (U.S. Patent 6,606,796 issued August 19, 2003); accession file.

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