The octant has an ebony frame and limb with a black-lacquered brass index arm and fittings. It has inlaid ivory plates on the crossbar and on the back of the frame. There is no tangent screw and the clamping screw is located on the back of the index arm. The octant has three index shades, two in red and one in green. Index-glass adjustment is made by a screw and on the horizon glass by a lever, wing nut and a milled clamping screw. The sight vane has two pinholes and a swivelling shade with its glass missing. A pencil or screwdriver is missing from the crossbar. The octant is contained in a shaped polished mahogany box, with a trade label in the lid for Alexander Alexander, Optician (established in 1828), 6 High Street, Exeter (his address in 1834).

The instrument has an inlaid ivory scale from -2° to 100° by 20 arcminutes, measuring to 92°. The octant has an ivory vernier measuring to 1 arcminute, with zero at the right.