Prewett Addograf
date: label: date made
content: 1940
label: date made
content: 1920s?
name: label: maker
content: Prewett System Company
notes: label: Description
content: This aluminum device consists of two discs sealed together at the rim, with a rotating disc in between. Various numbers are stamped around the rim of the rotating disc. Openings in the outer discs reveal three numbers on either side at one time. One side of the instrument has the numbers from 1 to 20 stamped clockwise around the scalloped rim of the movable disc. The other side of this disc has the numbers from 21 to 40, also stamped clockwise.
label: Description
content: At the top of the instrument, three alternate numbers are visible (i.e., 1, 3, 5). Three alternate numbers also are visible on the reverse side (i.e., 35, 37, 39). The sum of two numbers on opposite sides of the disc is always 40 (i.e., 1 and 39). Part of the scalloped edge of the movable disc is exposed at the bottom.
label: Description
content: Clay W. Prewett and the Prewett Addograf and System Company (also known as the Prewett System Company) of Los Angeles, California, sold this device. A 1940 brochure describing “The Prewett Addograf and System” indicated that it consisted of not only this instrument but a $10 brochure describing how it worked, a $5 brochure on modern short cuts in multiplication, division, interest, fractions, and mixed numbers; and a $5 multiplication chart. The entire system could be purchased for $15. It was not returnable.It is quite possible that this particular example dates to the 1920s, as Locke first gave away his collection in that decade.
label: Location
content: Currently not on view
place: label: place made
content: United States: California, Los Angeles
topic: label: Subject
content: Mathematics
setName: label: See more items in
content: Medicine and Science: Mathematics
label: See more items in
content: Adder
label: See more items in
content: Science & Mathematics
creditLine: label: Credit Line
content: Gift of L. Leland Locke
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: MA.155183.28
label: catalog number
content: 155183.28
label: accession number
content: 155183
objectType: label: Object Name
content: adder
physicalDescription: label: Physical Description
content: aluminum (overall material)
label: Measurements
content: overall: .5 cm x 7.5 cm x 7 cm; 3/16 in x 2 15/16 in x 2 3/4 in