Controller Circular Slide Rule for Canadair

This aluminum circular slide rule has a D scale on the base and C, CI, and A scales on the rotating disc. (These scales are not marked with letters.) Parts of the D and C scales are shaded in blue and yellow, and the CI scale is printed in red. A clear plastic rotating indicator is fastened with an aluminum screw and nut. The center of the rotating disc is marked: CONTROLLER, and a black arrow indicates the origin point.

The back of the instrument has a ruler around the serrated edge, marked by single centimeters from 0 to 20. Between the numbers 0 and 20 is marked DBGM, which stands for "Deutsches Bundes Gebrauchsmuster," or German Federal Registered Design. This indicates the device was made in West Germany after 1949. Inside the ruler is a chart shaped like a wheel, for making conversions between various weights and measures. The center is marked: MADE IN GERMANY (/) © (/) CONTROLLER (/) MÜNCHEN 15. Controller manufactured a few types of circular slide rules in Munich in the second half of the 20th century. This instrument most closely resembles Controller's model Mod 75 R.

The slide rule fits in a round, dark blue plastic sleeve. The sleeve is marked: C-L (/) CANADAIR LIMITED. The instrument was probably distributed as a promotional item by Canadair, an aircraft manufacturer established in 1944 that was the Canadian subsidiary of General Dynamics from 1954 to 1976, when it was nationalized. The company was acquired by Bombardier Inc. in 1986. The slide rule was probably made around 1960.

References: Peter M. Hopp, Slide Rules: Their History, Models, and Makers (Mendham, N.J.: Astragal Press, 1999), 154; "Herman van Herwijnen's Slide Rule Catalogue at ISRM – C," http://sliderulemuseum.com/HSRC/SRC_C.htm; James Marsh, "Canadair Ltd.," The Canadian Encyclopedia, http://thecanadianencyclopedia.com/articles/canadair-ltd.

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