Grey painted brass. Fitted with a large prism having a black engraved vertical line at centre and a "V" sight at top, adjusted by a milled knob at side. Provided with two rectangular dark shades, a black glass reflector, and a spirit level. a curved steel reflector is mounted on circle below prism. A counter -balance weight is fitted on circle opposite to the prism. A thread and two small brass bars (to check setting of prism) are contained in lid of box.