The quintant has a grey-green lacquered brass frame, with a circular brass handle. There is no tangent screw or other device for a slow motion of the two index arms. The upper clamping screw is located on the front of the index arm and the lower clamping screw is on the back of the arm. The instrument has no shades. It has two index glasses, which are adjusted by screws and on the one large horizon glass, with two silvered portions and clear glass in-between, it is by a screw and a capstan screw.

Attached to the quintant are two single lens magnifiers. The upper magnifier is on a 50mm swivelling arm and the lower magnifier is on a 60mm swivelling arm. There is also a threaded telescope bracket with perpendicular adjustment made by a rising-piece and a milled knob. The telescope is 70 mm in length with an erect image and a green shaded eyepiece.

The instrument has a polished brass limb with two parallel inlaid silver scales; the lower from the left from 0° to 155° by 30 arcminutes, measuring to 147°, the upper from the right from 0° to 150° by 30 arcminute, measuring to 144°. The quintant has two silver verniers measuring to 1 arcminute, with zero at the left on the lower, and at the right on the upper.

The quintant is contained in a square fitted mahogany box, marked on a brass plate inlaid in the lid, ‘Da.92’.

Invented by Rear-Admiral Frederick William Beechey (1796-1856). The instrument can be used to measure the angles between three objects at once. When both index arms are set at 0°, the index glasses are exactly parallel. Compare with NAV1120. ‘Da.92’ possibly refers to the numbering adopted by the Hydrographic Office in February 1828, whereby the letter D was given to sextants.