The octant has an ebony frame and limb with a brass index arm, fittings, and a wooden handle. It also has inlaid ivory plates on the crossbar and on the front of the frame; the latter is probably a replacement. The tangent screw and clamping screw are located on the back of the index arm. The octant has two socket shades in red and green, both of which are cracked. The horizon shades are missing. Index-glass adjustment is made by a screw and on the horizon glass by a lever, worm gear and a milled clamping screw. The reflecting areas of the glasses are silvered paper and are replacements of the originals. Attached to the octant is a threaded, non-adjustable telescope bracket. The telescope or swivelling sight vane is missing. The octant has no box.
Provenance Discovered in Basin No. 4, Portsmouth Dockyard, by Petty Officer Morley in 1968. Presented by Mr Mortimer, Receiver of Wrecks, H.M. Customs and Excise, Customs House, Plymouth, Devon, in 1974.

The instrument has an inlaid ivory scale from -4° to 108° by 20 arcminutes, measuring to 90°. The octant has a cracked ivory vernier measuring to 30 arcseconds, with zero at the right.

Although the instrument is relatively heavy the large glass suggests this was a surveyor’s octant. The Emanuels were goldsmiths and jewellers, and possibly only the retailers rather than the makers of this instrument.