The octant has an ebony frame and limb with a brass index arm, fittings, and a brass stop for the index arm. It also has inlaid ivory plates on the crossbar and on 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 three socket shades, two red, and one green. 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, whereas the back sight vane has one pinhole. A screwdriver is fitted in the crossbar. The octant is contained in a stepped oak box, containing in the lid a handwritten label, ‘Chapman Light Yarmouth 1906’.

This instrument is unsigned, but has a scale mark for Spencer Browning and Rust. It may therefore be assumed that they are the makers.

It has an inlaid ivory scale from -2° to 99° by 20 arcminutes, measuring to 91°. The octant has an ivory vernier measuring in 1°, with zero at the right.