Graduations-Semi-circle graduated 0-180, and 180-0, and carries a diagonal scale. The alidade 10.4" (26.5cm) long, has a fiducial edge at each end. A suspension ring is attached to upper part of semi-circle and there is a straight edge 11.2" (28.4cm) long at the lower part. A balla nd socket head and a square plate 4.25" x 4.25" (10.8 x 10.8cm) are attached to back of instrument.
Sights-There are location holes for two sight vanes in straight edge. Two sight vanes 1.4" (3.5cm) long, mounted on alidade, each having a hole (one with cross bar missing) with straight edge sights above.
Compass Dia. 3.6" (9.2cm) mounted at centre of instrument. Fitted with a narrow blued steel needle in form of an arrow 2.9" (7.3cm) long, with a brass pivot cap at centre. Graduated to 32 points and to 360 degrees.