The sextant has a mahogany frame and limb with a brass index arm, fittings, and a brass stop for the index arm. It has an inlaid plate in the crossbar, which is missing. The double-ended tangent screw is located on the front of the index arm and the clamping screw, which is a modern replacement, is on the back. The sextant has three index shades, one green and two red, and no horizon shades. Index-glass adjustment is made by a screw and on the horizon glass, with its glass broken, by a lever, wing nut and a clamping screw. Attached to the sextant is a threaded telescope bracket with perpendicular adjustment by a rising-piece and a milled knob. The telescope is 74 mm in length with an erect image, and is in a wooden barrel. The sextant has no box.

The instrument has an inlaid ivory scale from -2° to 129° by 20 arcminutes, measuring to 119°. The sextant has an ivory vernier measuring to 1 arcminute, with zero at the right.

The scale mark indicates that the instrument was divided on Ramsden’s engine.