Acreage Worked Circular Slide Chart by Perrygraf for Allis-Chalmers

The base of this orange, black, and white cardboard circular chart has scales for the number and size of plows and for the size of combines, planters, or harrows. Riveted to the rectangular base is a disc with a scale of tractor speed in miles per hour. Setting the dial for the appropriate tractor speed opposite the size and type of machinery employed reveals the approximate number of acres worked per day.
According to its markings, Perry Graf Corporation of Maywood, Ill., copyrighted this "Tractor Calculator" in 1938 and made it for the Allis-Chalmers Manufacturing Company's Tractor Division in Milwaukee, Wis. A curator's note indicates the copyright was not issued until November 27, 1941. Perrygraf (spelled variously as "Perrygraf" and "Perry Graf") designed special purpose "slide charts," which were often distributed by manufacturers to their customers.
The back of the calculator contains an advertisement for Allis-Chalmers, titled: WORK-PER-DAY THE A-C WAY. For other rules distributed by Perrygraf, see 1983.3009.06 and 1996.3029.01.
Currently not on view
Object Name
calculating rule
slide rule
date made
ca 1941
Perry Graf Corporation
Physical Description
metal (part material)
paper (overall material)
overall: 9.5 cm x 9.5 cm x .1 cm; 3 3/4 in x 3 3/4 in x 1/32 in
place made
United States: Illinois, Maywood
ID Number
catalog number
nonaccession number
Rule, Calculating
Promotional Item
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Slide Rules
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Transfer from Smithsonian Institution Libraries
Additional Media

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