Safe-T Pro>Ruler Combination Protractor, Triangle, and Ruler, Group of 2

These clear plastic objects are two different sizes of the same instrument. Each instrument consists of two rectangular pieces with half-discs at one end. The pieces are held together at their curved ends with a metal thumbscrew, so the instrument resembles a sector. The top half-disc has a magnifier for reading from the scale of degrees, numbered by tens from 180 to zero, around the edge of the bottom half-disc. Besides measuring angles, the protractor may be used to open the rectangular pieces to a desired angle. Then, an angle or triangle may be drawn along the inside edges, which are marked with a centimeter scale divided to millimeters.
The outer edge is also marked with a centimeter scale that may be used by fully opening the instrument. The larger instrument has an overall width of 60cm, and the smaller instrument is 30cm across. The device can draw and measure lines and measure three-dimensional angles.
The larger instrument is marked: PRO > RULERTM #43052 (/) SAFE-T PRODUCTSTM, Inc. (/) LaGrange, IL 60525-0692. One of the flat ends is stamped with the number 2, and the other flat end is stamped with the number 3. The smaller instrument is marked: PRO > RULERTM by SAFE-TTM (/) #43051 (/) View-ThruTM SAFE-T PLASTICTM (/) LaGrange, IL 60592-0692. Both of the flat ends are stamped with the number 2.
The larger instrument is in a plastic envelope with instructions on the back. The back is marked: Made in Taiwan. It is also marked: PATENTED U.S., R.O.C., AUSTRALIA, GERMANY AND P.R.C. The smaller instrument is in a plastic envelope with a paper sheet of instructions. This sheet is marked: Made in Taiwan. It is also marked: PATENTED R.O.C., AUSTRALIA, GERMANY AND P.R.C. U.S. AND CANADIAN PATENTS PENDING. Thus, the smaller instrument is probably slightly older than the larger one. The patents were not identified, but the donor reported that the inventor was from Taiwan.
Extra Measures, Inc., distributed this instrument in the United States. In 2000, model number 43051 sold for $3.50, while the "jumbo" sized model number 43052 sold for $18.95. For company history, see 2000.0160.04.
Reference: accession file.
Currently not on view
Object Name
scale rule and protractor
date made
ca 2000
associated date
Extra Measures, Inc.
Safe-T Products, Inc.
Physical Description
metal (overall material)
paper (overall material)
plastic (overall material)
overall: 1.8 cm x 34.4 cm x 6.2 cm; 23/32 in x 13 17/32 in x 2 7/16 in
place made
associated place
United States: Illinois, Bensenville
ID Number
accession number
catalog number
Scale Rules
Science & Mathematics
Rule, Measuring
Drawing Instruments
See more items in
Medicine and Science: Mathematics
Scale Rules
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Extra Measures, Inc.
Additional Media

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