The sextant has a polished brass frame with a wooden handle. The tangent screw and clamping screw are located on the back of the index arm. The index glass is black rather than silvered and for use with Sun and Moon observations only. This must be a replacement as the instrument was originally fitted with shades, which are unnecessary with black glass, and there is no trace of a Maskelyne flap. The sextant has three red shades and two red horizon shades. Index-glass adjustment is made by a screw and on the horizon glass by a fixed milled key. Attached to the sextant is a telescope bracket without adjustment and a sight-tube mounted between the telescope bracket and the horizon glass mounting. The sight-tube has a rotating variable shaded eyepiece with a choice of two red shades. The sextant is contained in a fitted wooden box.

The instrument has a brass scale from -2° to 137° by 20 arcminutes, measuring to 121°. The sextant has a brass vernier measuring to 30 arcseconds, with zero at the right.

A telescope similarly mounted is found on a sextant by Ramsden preserved in the Whipple Museum of the History of Science in Cambridge (inv. no. Wh.2122).