The Engineers Slide Rule, made in USA by E. M. Scofield, Bridge Engineer, Youngstown, Ohio. Patent 1901-1902. Comprised of paper scales on boxwood. 24" L x 2" W x 1/2" D. Provenance: Private West Tennessee Collection. Note: According to the Smithsonian Museum of American History, which has an identical example in its collection, "Edson Mason Scofield (1867-1939) developed this rule in 1891 while he worked for Edwin Thacher (inventor of the cylindrical slide rule bearing his name). Thacher applied for a patent on the design in 1900 and assigned a half-interest to Scofield when the patent was issued in 1901. According to the instrument, Scofield may have distributed the rule himself." CONDITION: Shows staining and toning due to age and use.