The sextant has an anodized brass frame and a wooden handle with a brass-lined hole for the locking mechanism. The endless tangent screw and clamping screw are positioned on the back of the index arm. The sextant has four green shades, a Wollaston prism, and three green horizon shades. Index- and horizon-glass adjustment is made by capped capstan screws.

Attached to the sextant is a magnifier on an 80mm swivelling arm with a frosted glass shade. There is also a threaded telescope bracket in two parts, fitted for correcting collimation error. It has perpendicular adjustment made by a clamping screw. The telescope is 219 mm in length with an inverted image and large objective lens. A second telescope is 179 mm long with an inverted image. A third telescope is 73 mm long with an erect image (star finder). A fourth is 180 mm long with an inverted image and four cross wires. An extra drawtube in 70 mm long but is incomplete. The sight-tube is 82 mm in length with two shaded eyepieces in green and mauve, two L-shaped brackets, a patent greater angle clamp, a screwdriver, and an adjusting spanner.

The instrument has a polished brass limb with inlaid silver scale from -5° to 156° by 10 arcminutes, measuring to 131°. The sextant has a silver vernier measuring to 1 arcminute, with zero at the right.

The sextant is contained in a square fitted wooden box with a patent locking mechanism for securing the instrument when not in use, and a blank inlaid brass plate on the lid. There is a National Physical Laboratory certificate of examination, dated January 1921 in the lid.

The Wollaston prism was used for star observations at night, when the horizon was not well defined. It produces two images of a star, one above, the other below the original position of the star, with the horizon exactly in between them.