The octant has an ebony frame and limb with a brass index arm and fittings, a brass stop for the index arm and inlaid ivory plates on the crossbar and the back of the frame. There is no tangent screw and the clamping screw is positioned on the back of the index arm. The octant has two sets of three socket shades, two red and one green on the first set and one red, one orange, and one green on the second. One set is probably from another instrument. Index-glass adjustment is made by a screw and on both horizon glasses by levers, wing nuts and milled clamping screws. The sight vane has two pinholes and a swivelling shutter and the back sight vane has one pinhole. A pencil or screwdriver is missing from the crossbar. The octant is contained in a stepped keystone oak box, marked on the lid Alfred Terry, which was probably an owner’s name.

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.