The octant has an ebony frame and limb with a brass index arm and fittings. It also has a wooden handle and an inlaid ivory plate on the crossbar. The tangent screw and clamping screw are on the back of the index arm. The octant has four socket shades, three 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 lever, a milled screw and worm gear. A magnifier is attached to the octant on an 83mm swivelling arm as well as a threaded telescope bracket without adjustment. The telescope (88 mm), erect image, may perhaps be from a different instrument. The sight-tube (94 mm) has a red shaded eyepiece; however, the adjusting pin and a second eyepiece are missing. The octant is contained in a mahogany keytone box, with a trade label in the lid for ‘John Lilley and Son, Jamaica Terrace, Commercial Road’ near the West India Docks, London (1846-65). An incomplete blank mother-of-pearl plate is inlaid on the top of the lid.

Inlaid ivory scale from -2° to 106° by 20 arcminutes, measuring to 91°. The octant has an ivory vernier measuring to 30 arcseconds, with zero at the right.