Plotting Scale

This two-sided boxwood rule has a scale of chords and architect's scales dividing the inch into 40, 35, 30, 25, 20, and 15 parts on one side. A white sticker on that side is marked: 783. The other side has an inch scale divided to 1/10" and numbered by ones from 1 to 6; a scale divided to ones and numbered by tens from 10 to 50 (10 units is approximately 3 cm); and 5" plotting scales with diagonal scales at each end. One plotting scale is divided to 1/2" and numbered by ones from 10 to 1, and the other is divided to 1/4" and numbered by ones from 1 to 18. One edge of the rule is scalloped.

The previous owner collected more than 1,200 hand tools and machine tools and displayed them at his family's building company in Baltimore, Md. This object was item number 783 in his collection. It probably dates to the turn of the 20th century. Similar scales were sold for 10¢ to 15¢ by Dietzgen (model number 1690) from at least 1902 to 1912 and by Keuffel & Esser (model number 1616) from at least 1892 to 1913. Both companies stopped advertising the object before 1921.

References: Catalog of Eugene Dietzgen Co., 6th ed. (Chicago, 1902), 135; Catalog of Eugene Dietzgen Co., 7th ed. (Chicago, 1904), 162; Catalog of Eugene Dietzgen Co., 9th ed. (Chicago, 1910–1912), 207; Catalogue of Keuffel & Esser Co., 23rd ed. (New York, 1892), 126; Catalogue of Keuffel & Esser Co., 33rd ed. (New York, 1909), 189; Catalogue of Keuffel & Esser Co., 34th ed. (New York, 1913), 184.

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