Charvoz-Roos SR-104 Simplex Slide Rule

This ten-inch wooden one-sided rule is painted white. A, D, and K scales are on the base; B, CI, and C scales are on the front of the slide; and S, L, and T scales are on the back of the slide. The top of the base is marked in red: No. SR-104 CHARVOZ-ROOS MADE IN U. S. A. On the back of the base are tables of equivalents and settings that show where to place the slide in order to convert between various units, such as from centimeters to inches. There is no indicator. The instrument fits in a black paper case that was once coated with synthetic leather.

Brief articles in the New York Times indicate that the firm of Charvoz-Roos was formed in New Jersey in 1946 and apparently closed in 1953. See also 2009.3008.01. This company rebranded slide rules by other manufacturers and assembled slide rules from parts made by other manufacturers. This rule resembles a rule made by the Lawrence Engineering Service (1983.0042.01), but the tables on the back are like those based on National Bureau of Standards Circular No. 47 that Keuffel & Esser put on its rules from the 1920s to the 1950s. See 1984.1068.01. Although 1987.0184.01 is a painted wooden rule with these tables, the style of the letters and pi symbols on the scales are different from those on this rule.

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