Graduations-Semicircle graduated 0-180, 180-0. The alidade 9.75" (24.8cm) long has a vernier scale at each end, graduated 0-60 by 5'. There is a straight edge 11.5" (29.3cm) long at the lower part of instrument. A ball and socket head and a square plate 4.1" x 4.1" (10.5 x 10.5cm) are attached to back of instrument.
Sights-Two sight vanes 2.2" (5.5cm) 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. A rectangular sighting slit 2.6" (6.5cm) long (complete with thread) is cut in straight edge at left hand end. Two sight vanes 2.4" (6cm) long mounted on alidade; one sight with a vertical slit and rectangular aperture above (complete with thread), the other with a rectangular aperture (complete with thread) with a vertical slit above. A rectangular sighting slit 2.75" (7cm) long (complete with thread) is cut in the alidade at right end.
Compass-Dia 3.5" (9cm) mounted at centre of instrument. Fitted with a tapered edge bar needle 2.9" (7.5cm) long, with a jewelled pivot cap at centre. Graduated to 8 points and to 360 degs.
In fitted wooden box lined with red baize.