Standard issue item as used by Australian servicemen during the conflict in Vietnam. A plotting board is a mechanical device used as part of a firing control system to track the observed course of a target, project its future position, and derive the azimuth (or direction) and range needed to direct the fire of the guns of a battery to hit that target.White plastic base. A circle marked with grid lines is printed on the base and a vernier for finding azimuth deflections in along top edge. Rotating disc pivots at the centre atop the disc with distances measured radially form 0 at the centre to 3400 metres around the rim range form 0-6400 metres. A scale pivoted at the centre assists in reading distances.Nth and Sth top and bottom on rotating disc. East and West in centre distances in black on outer of disc. Distances in green on inner North, South, East, West. Varn W left bottom of disc. varn E on right bottom of disc.plotting board, m16