The sextant has an ebony frame and limb with a brass index arm and fittings, wooden handle, and an inlaid ivory plate in the crossbar. The tangent screw is located on the front of the index arm, and the clamping screw is on the back. The sextant has four shades, three red and one green, and three horizon shades, two red and one green. Index-glass adjustment is made by a screw and on the horizon-glass by a screw, lever, worm gear and a milled screw.

Attached to the sextant is a threaded telescope bracket with perpendicular adjustment made by a rising-piece and a milled screw. The telescope is 125 mm in length with an inverted image and two parallel cross wires. The sight-tube is 79 mm in length. The sextant is contained in a wooden keystone box, with a trade label for William Parnell, 94 near the Bridge, Lower East Smithfield, London (1816-39).

The instrument has an inlaid ivory scale from -2° to 134° by 20 arcminutes, measuring to 120°. The sextant has an ivory vernier measuring to 30 arcseconds, with zero at the right.