Bowl-Black painted brass, two filler plugs at side. Base of bowl fitted with a glycerine filled domed glass balancer. Inside of bowl painted black with a black wire lubber line mounted against a white painted strip on side of bowl. Verge ring graduated 0-180 degs. Verge glass is fitted with a socket at its centre to accommodate an azimuth instrument. Fitted with fore-and-aft gimbal pivots which have brass roller bearings.
Card-Dia. 6.9" (17.5cm) Mica (?) painted black with white markings, graduated to 1/4 points and quadrantally in degrees. Attached to a black float at centre.
In wooden box 12.6 x 12.6 x 9.2" (32 x 32 x 23.2cm)