The sextant has a polished brass frame with alloy fittings and a wooden handle. The tangent screw is located on the front and the clamping screw is on the back of the index arm. The sextant has three shades, two red and one green, and three horizon shades, two red and one green. Index-glass adjustment is made by a screw and on the horizon glass by a milled knob, an extended lever and a clamp operated from beneath the telescope bracket.

Attached to the sextant is a threaded telescope bracket in two parts, which is fitted for correcting collimation error. It has perpendicular adjustment by a rising-piece and a milled knob. The telescope is 131 mm in length with an inverted image and cross wires, which are broken. A second telescope is 122 mm in length with an erect image. The star finder is 85 mm in length with an erect image; this is a modern addition to the instrument. The sight-tube is 89 mm in length.
The sextant is contained in a keystone polished mahogany box, with the trade labels for H.C. Blair (late Blair and Son), 45 Prince Street, Bristol, for William Gerrard, 35 South Castle Street, Liverpool (1862-90), and a label for ‘1908 Essex Regt. Edgar T. Adams Secundo Inter Omnes D.D.’.

The instrument has a polished brass scale from -2° to 130° by 20 arcminutes, measuring to 128°. The sextant has a brass vernier measuring to 1 arcminute, with zero at the right.

Peter Dollond patented the horizon glass adjustment (no. 1017 of 1772).