Mahogany and brass octant.

Octant made by John Gilbert, London, 1764. Mahogany frame, limb, and index arm; the lower end of the arm is of brass, brass fittings, a brass stop for the index arm; an inlaid ivory plate in the crossbar. Signed on the inlaid plate: Made by In.o Gilbert on Tower Hill | LONDON | For Iere.h Beale, Feb.ry 27: 1764. Inlaid ivory scale from -5° to 95° every 20', measuring to 90°. Ivory vernier to 1', zero at the centre. There is no tangent screw; the clamping screw is on the back of the index arm (its brass pressure plate is broken). Three socket shades (two red, one green), from another instrument. Index-glass (broken and separated from the instrument) adjustment by screw; adjustment of the horizon glass by a fixed milled screw and a lever, worm gear and a milled clamping screw. The sight vane has one pinhole. No box.