Around 1970 many American companies and government agencies encouraged Americans to adopt the metric system. Regal Beloit of Wisconsin and other manufacturers of cutting tools and gear boxes adopted the units of measure and distributed devices like this one to assist in their use.
The one-sided white cardboard rule is printed in orange and black and has eight windows. Two logarithmic scales on the slide are viewed through four of the windows so that the user can convert between yards or feet and meters; centimeters and inches; pounds and kilograms; and tons and metric tons. Two more logarithmic scales on the slide permit conversions between square yards and square meters; square centimeters and square inches; cubic yards and cubic meters; and liters and imperial gallons or U.S. gallons. Below the windows is a scale for converting between Celsius and Fahrenheit temperatures. The rule is marked: REGAL BELOIT. It is also marked metric/inch (/) CONVERTER. It is also marked SWANI PUBLISHING COMPANY (/) P.O. Box 284 • Roscoe, Illinois 61073 (/) 815 / 389-3065.
Impact was presumably a printing company. Swani was a division of Regal Beloit that published a few elementary textbooks on the metric system. Compare this rule to 1990.0689.01.