Safe-T Semicircular School Protractor


This clear plastic semicircular protractor arrived at the Smithsonian in a clear plastic wrapper, which is stored with it. Designed for use by schoolchildren, it contains four sets of divisions, three to single degrees and the innermost one to ten degrees.

The outer two divisions are marked by tens for reading left-opening angles, from 0° to 180°. The inner two divisions are marked by tens for reading right-opening angles, from 170° to 0°. A semicircular slot separates the two scales.

The interior of the protractor is open. A scale along the bottom edge of the opening is divided to millimeters and marked by centimeter from 0 to 10. The outer bottom edge of the protractor is divided to sixteenths of an inch and is marked by inches from 1 to 6. The corners are slightly rounded.

The object bears several marks along its diameter edge: PAT. [/] PENDING; SAFE-T TM [/] PRORUCTS [sic] Inc.; Angles Opening Left (>) [/] Use Upper Scale; VIEW-THRU TM [/] SAFE-T PLASTIC TM [/] #45780; Angles Opening Right (<) [/] Use Lower Scale; La Grange, IL [/] 60525-0692.

Reference: SAFE-T Products, Inc., Innovative Safe Drawing and Measuring Instruments, about 1998. According to this catalog, these protractors sold individually for 75 cents. In 2006, the company became a subsidiary of A. Daigger & Company and its name changed to Classroom Products Warehouse.

Date Made: 1998

Maker: Safe-T Products, Inc.

Location: Currently not on view

Place Made: United States: Illinois, La Grange

Subject: MathematicsEducation, High School


See more items in: Medicine and Science: Mathematics, Science & Mathematics, Protractors


Exhibition Location:

Credit Line: Collected at the American Mathematical Society annual meeting, 8 January 1998

Data Source: National Museum of American History

Id Number: 1998.0033.02Catalog Number: 1998.0033.02Accession Number: 1998.0033

Object Name: protractor

Physical Description: plastic (overall material)Measurements: overall: .1 cm x 15.8 cm x 8.5 cm; 1/32 in x 6 7/32 in x 3 11/32 in


Record Id: nmah_694146

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