Gerber Variable Scale, Model TP007100B

This rectangular aluminum instrument has a scale of reciprocal inches, unevenly divided and labeled RI; a scale of equal parts, labeled I and numbered by ones from 1 to 10 and by tens from 15 to 95; and a logarithmic scale labeled L10. An aluminum slide on top of the scales has a plastic indicator with a hairline. The slide is attached to a spring that expands and contracts within a clear plastic housing above the scales. It has 103 coils, 100 of which are calibrated. Every tenth coil is colored red, every fifth coil is blue-green, and the rest are white. A second spring is numbered by twos from 0 to 10.
Below the scales is marked: THE GERBER SCIENTIFIC INSTRUMENT COPMANY HARTFORD, CONN. GERBER VARIABLE SCALE ® MODEL TP007100B U.S. PAT. NO. 2843935 U.K. PAT. NO. 845215 MADE IN U.S.A. A brown leather case is lined with black velvet marked: The Gerber Scientific Instrument Co. (/) Hartford, Connecticut. A small manila envelope inside the case holds an Allen wrench. The case fastens with Velcro and slides into a white cardboard box.
The instrument allows users to read off points along a plotted equation without having to draw the curve. It can also be used to convert between proportional scales, for instance when enlarging or reducing an engineering drawing. Heinz Joseph Gerber (1924–1996) invented the device while he was studying aeronautical engineering at Rensselaer Polytechnic Institute in 1945, a few years after escaping Nazi-controlled Austria with his mother. He and a partner established the Gerber Scientific Instrument Company in Hartford, Conn., to manufacture the Gerber Variable Scale. Gerber ultimately held about 650 U.S. and foreign patents for calculating instruments, digital drafting machines, and robotic and electronic manufacturing systems for products from electronics to textiles. The firm was renamed Gerber Scientific, Inc., in 1978.
Compare to 1994.3104.01. For an instruction manual, see 1994.0113.04.
References: Arthur Bartlett, "A Quick Spring to Success," Nation's Business (October 1949): 43–45, 62–64; Heinz Joseph Gerber, "Instrument for Measuring, Interpolating, Plotting and the Like" (U.S. Patent 2,843,935 issued July 22, 1958); "Our Founder," Gerber Scientific,
Currently not on view
Object Name
calculating rule
scale in case
date made
ca 1980
Gerber Scientific Instrument Company
Physical Description
aluminum (overall material)
plastic (overall material)
leather (overall material)
fabric (overall material)
cardboard (overall material)
velcro (overall material)
overall: 3 cm x 33.1 cm x 7.4 cm; 1 3/16 in x 13 1/32 in x 2 29/32 in
place made
United States: Connecticut, Hartford
ID Number
accession number
catalog number
Scale Rules
Science & Mathematics
Rule, Calculating
See more items in
Medicine and Science: Mathematics
Scale Rules
Data Source
National Museum of American History, Kenneth E. Behring Center
Additional Media

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