The octant has an ebony frame and limb with a dark brown-lacquered brass index arm and fittings. It also has an inlaid ivory plate on the crossbar. The tangent screw and clamping screw are positioned on the back of the index arm. The octant has three index shades, two red and one 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 shutter. A pencil or screwdriver is missing from the crossbar. The octant is contained in a keystone polished mahogany box, with a trade label in the lid for J. D. Potter (successor to R. B. Bate), 31 Poultry, London, and a circular handwritten label ‘E. T. A. from Helen, Francis, Isabel, Gordon, & Pauline, Christmas 1909’.

The instrument has an inlaid ivory scale from -3° to 109° by 20 arcminutes, measuring to 93°. The octant has an ivory vernier measuring to 1 arcminute, with zero at the right.