Bowl-Copper painted brass, with oil-filled chamber at base. Inside of bowl painted white, with black painted lubber line extending from centre to rim. Anodised brass verge ring graduated from N to S on each half 0o - 180o. Flat verge glass is fitted with a brass bush at the centre, on which an azimuth mirror could pivot. Lower part of bush prevents card from lifting off pivot point. Two knife-edged gimbal pins are fitted to the bowl in fore and aft positions.
Pivot-Brass needle located in socket of pivot stem attached to base of bowl.
In fitted oak box 12.5 x 12.5 x 9.25" (31.7 x 31.7 x 23.5cm)