This sight consists of an open rectangle with a cross bar at centre. This crossbar holds a brass stud which fits into the centre boss of the compass. The folding back sight has a slit and moveable spy hole. The folding fore sight is an open arch with thread. There is a spirit level at its base and a celestial reflector in front of it. There is a thread running down the fore sight and along the open rectangle. There are three brass pegs on underside.