The sextant has an anodized brass three-circle pattern frame and a wooden handle. The white plastic micrometer drum and a clamp are located at the bottom of the index arm. The instrument has four green shades and three green horizon shades. Index- and horizon-glass adjustment is made by capped capstan screws.

Attached to the sextant is a threaded telescope bracket in two parts, fitted for correcting collimation error. It has perpendicular adjustment made by a rising-piece and a milled knob. The telescope is 172 mm in length with an inverted image and four cross wires. A second telescope is 73 mm long with an erect image and a wide objective lens (star finder). An extra drawtube is 96 mm long with two parallel cross wires. Accompanying the sextant is a sight-tube, which is 82mm in length, two green shaded eyepieces, an adjusting pin, and a spanner.

The instrument has a bronzed limb with an inlaid silver scale from -5° to 130° by 1°, measuring to 129°. Micrometer to 0.2 arcminutes.

The sextant is contained in a square fitted wooden box, with a National Physical Laboratory Teddington certificate of examination in the lid, dated 30 December 1939. There is an inlaid blank brass plate on the top of the lid.