The sextant has a black-lacquered brass curve-pattern frame and a wooden handle. The tangent screw and clamping screw are on the back of the index arm. The instrument has no shades. Index-glass adjustment is made by a capped screw and on the horizon-glass by a square-headed screw, a detached key and a capped screw.

Attached to the sextant is a magnifier on a 45mm swivelling arm. There is also a threaded telescope bracket without adjustment. The telescope is 77 mm in length with an erect image and a wide objective lens (star finder). It has a detached sight vane with one pinhole and a milled adjusting key.

The instrument has a polished brass limb with an inlaid silver scale from -5° to 155° by 30 arcminutes, measuring to 132°. The sextant has a silver vernier measuring to 1 arcminute, with zero at the right.

The sextant is contained in a square fitted wooden box marked ‘H.O. [broad arrow] 10’, and containing in the lid a trade label for Cary, Porter, Ltd, 7 Pall Mall, London. H.O. stands for Hydrographic Office

Originally on loan from Hydrographer of the Navy, Taunton.