Six inch circular protractor by John Troughton, in mahogany case, c.1785 Circular protractor, 1765-1770 1765-1770
Circular protractor 6-inch, engraved "Watkins and Hill Charing Cross London"; divided in degrees and numbered 0 to 360 degrees; in wood case with inlaid brass plate engraved "H.O. ^ 7" Circular brass protractor, 1818-1856 1818-1856
