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Surveyor's Vernier Compass
"B. Stancliffe - Philada Maker" and "Warranted"
length 14.125 inches; needle 5 inches
Benjamin Stancliffe (1782-1834) was born in England, apprenticed with his uncle, John Stancliffe, a noted instrument maker in London, and worked for Edward Troughton making sophisticated geodetic instruments for the fledgling United States Coast Survey. Stancliffe then migrated to America, appearing in Philadelphia directories as early as 1817. In 1828 he went into partnership with his former apprentice, Edmund Draper. By 1832 Stancliffe was again in business on his own, advertising that he manufactured "all kinds of mathematical, optical, and philosophical instruments," including surveyor's compasses, theodolites, sextants, and quadrants.
This compass has a variation arc on the north arm that extends 22 degrees to either side; the vernier is moved by rack and pinion, and reads to 5 minutes. There is a spirit level on the south arm. Since Stancliffe was capable of making a compass of this caliber, the meaning of the word "Warranted" is not clear.
Ref: Robert C. Miller, "Benjamin Stancliffe and His Successors: A Century of Mathematical Instrument Makers in Philadelphia," Rittenhouse 11 (1996): 1-13.