Perfection Self-Adding Ruler
date: label: date made
content: 1895
name: label: patentee
content: McClelland, Robert E.
notes: label: Description
content: The wooden ruler also serves as a stylus-operated non-printing adding machine. It has a plastic inset along the middle, with a perforated paper strip that moves below the plastic. The numbers from 1 to 45 are marked along one edge of the plastic and from 46 to 90 along the other. A small dial and a window are at one end. Instructions are given on a plastic insert on the reverse of the rule. The number in the window indicates units and tens, while those around the dial denote hundreds. Only one of the hundreds digits (3) is marked. There is no stylus. One edge of the ruler is beveled and has a brass insert. This edge is marked off with a scale 15 inches long, divided to 1/16 inches.
label: Description
content: The device is marked: PERFECTION (/) SELF-ADDING RULER (/) PAT. JAN. 8th 1895. No place of manufacture is indicated. The inventor, Robert E. McClelland, lived in Williamsville, Illinois. Later versions of the rule indicate that it was made in New York.
label: Description
content: Reference:
label: Description
content: Robert E. McClelland, “Computing Machine,” U.S. Patent 532241, January 8, 1895.
label: Location
content: Currently not on view
place: label: place patented
content: United States: Illinois, Williamsville
topic: label: Subject
content: Mathematics
setName: label: See more items in
content: Medicine and Science: Mathematics
label: See more items in
content: Adding Machines
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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.155183.30
label: accession number
content: 155183
label: catalog number
content: 155183.30
objectType: label: Object Name
content: adding machine
physicalDescription: label: Physical Description
content: paper (overall material)
label: Physical Description
content: plastic (overall material)
label: Physical Description
content: wood (overall material)
label: Physical Description
content: brass (overall material)
label: Measurements
content: overall: .8 cm x 38 cm x 4 cm; 5/16 in x 14 31/32 in x 1 9/16 in