The sextant consists of circular polished brass plates with a lid that when screwed on the back of the instrument serves as the handle. The index arm is moved by a milled knob on the upper plate. The sextant has two index shades, in red and green, which are moved by levers. There are no horizon shades. Index-glass adjustment is made by a screw and on the horizon-glass by a square headed screw, using a milled key shipped in the upper plate. Attached to the sextant is a single lens magnifier on a 75mm swivelling arm attached at the pivot. The sight-tube is 19 mm in length and is fitted in the body of the instrument. The sextant is contained in a leather case marked, ‘D.146’, with a sling strap.

The instrument has an inlaid silver scale from -5° to 152° by 30 arcminutes, measuring to 139° (the digits are read from the pivot). The sextant has a silver vernier measuring to 1 arcminute, with zero at the left.