Base-Brass semi-circle 7.5" (19cm) dia. Graduated 0-180, 0-180 degs by 30'. A ball and socket head is attached to underside of semi-circle at centre of straight edge.
Alidade-Length 7.5" (19cm), pivoted at centre of straight edge. Fitted with a fiducial edge at each end. A vertical open frame 4.5" (11.5cm) high is attached at centre of alidade. A plumb bob is suspended from top of frame on a two link chain.
Sight-A vertical heart-shaped plate is mounted at top of vertical frame, graduated 0-50, 0-50. A flat brass bar 8.3" (21.2cm) long, pivoted at its centre, is attached at centre of upper part of the plate. Fitted with a sight vane 2.5" (6.3cm) long at each end, each with a hole with brass cross sight and brass shutter with peep-hole.
In tooled leather case, lined with green hessian.