Graduations-Semicircle graduated 0-180, 180-0. The alidade 9.7" (24.5cm) long has a vernier scale at each end, graduated 0-60, to 30'. There is a straight edge 11.25" (28.6cm) long at the lower part of instrument. A ball and socket head and a square plate 3.9" x 3.9" (10 x 10 cm) are attached to back of instrument.
Sights-Two sight vanes 2.3" (6cm) long mounted on straight edge, one sight with a vertical slit with a rectangular aperture above (complete with thread), the other with a rectangular aperture (complete with thread) with a vertical slit above. Two sight vanes 2.6" (6.5cm) long mounted on alidade, one sight with a vertical slit with a rectangular aperture above (complete with thread), the other with a rectangular aperture (complete with thread) with a vertical slit above.
Compass- Dia. 3.6" (9cm) mounted at centre of instrument. Fitted with a tapered flat bar needle 2.9" (7.5cm) long, with a brass pivot cap at centre. Graduated to 16 points and quadrantally in degrees. Fitted with a needle locking mechanism which is operated by a milled knob at back of instrument.