Protractor by Jesse Ramsden Ten inch brass protractor, divided into 1/2 degrees and indented at 90°, 180°, 270° and 360° of the circular dial. Brass arms extend into the centre, dividing it into quadrants and a movable arm pivots from the centre, carrying a vernier, reading to one minute. This arm extends beyond the vernier, with a brass strip fastened to the top, a small hole visible at its end, which would have contained a sharp metal pin, to prick or mark angle points. A round hole is visible at the centre, where crosshairs would have been placed to mark the origin point for measuring angles. Engraved 'Ramsden London' and 'R.S. 61' across the immovable arms. 18th century