Safe-T 42123 Blackboard Open Triangles

These white plastic drawing instruments are blackboard-sized versions of Safe-T's set of two medium triangles, which were sold under various model numbers. A version of the set of two small triangles is ID number 1998.0033.01 in the mathematics collections. Both of these triangles have rounded corners, triangle cutouts in their interiors, and slots for drawing the template of a triangle around the cutouts. The triangles are marked: U.S. Pat. No. 5,419,054. They are also marked: VIEW-THRUTM; SAFE-T TRIANGLETM (/) Bensenville, IL 60106-0316; SAFE-T PLASTIC®. Each angle is marked with its measurement.
The 17-3/4"30°-60°-90° triangle is also marked: 42121. On the long leg, it has a scale representing inches, divided to 1/16" for two inches and to 1/10" for three inches and numbered by ones from 1 to 5. The short leg has a scale representing centimeters that is divided to millimeters and numbered by ones from 0 to 8. The 12-7/8"45°-45°-90° triangle is also marked: 42122. One leg has a scale representing inches, divided to 1/16" for two inches and to 1/10" for two inches and numbered by ones from 1 to 4. The other leg has a scale representing centimeters that is divided to millimeters and numbered by ones from 0 to 9.
The related companies, Safe-T Products, Inc., and Extra Measures, Inc., were established in the northwest Chicago suburbs in 1992 and 1997, respectively, to sell drawing instruments that were safe for children. J. Bruce Stoneberg, who subsequently became president of Extra Measures, Inc., received a patent for this design of a plastic triangle, with safe, rounded edges, in 1995.
Catalogs from 1998 and 2000 indicate that in 2000 Safe-T began making blackboard-sized triangles and selling them in sets of two under model number 42123 for $18.95. They were manufactured from a shatter-proof k-resin plastic patented and produced by Phillips Petroleum in Texas. In 2006 Safe-T was absorbed into Classroom Products Warehouse, and in 2007 Extra Measures was taken over by Learning Resources, Inc. These firms were next-door neighbors in Vernon Hills, Ill., as of 2012.
References: accession file; J. Bruce Stoneberg, "Triangular Drafting Instrument" (U.S. Patent 5,419,054 issued May 30, 1995); SAFE-T Products, Inc., Innovative Safe Drawing and Measuring Instruments, about 1998; Safe-T/Basics by Extra Measures, Inc., about 2000; "Corporate and Limited Liability Company Name Search," Office of the Secretary of State for the State of Illinois,
Currently not on view
Object Name
triangles, group of 2
date made
Safe-T Products, Inc.
Physical Description
plastic (overall material)
overall: 45.6 cm x 27.2 cm x 3 cm; 17 15/16 in x 10 23/32 in x 1 3/16 in
place made
United States: Illinois, Bensenville
ID Number
accession number
catalog number
Squares and Triangles
Science & Mathematics
Drawing Instruments
See more items in
Medicine and Science: Mathematics
Squares and Triangles
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Extra Measures, Inc.

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