Bowl- Diameter 6.5"(16cm) Grey painted aluminium bowl, expansion chamber at base (below domed cover). The top cover plate has a hole 1" (2.5cm) dia. through which a section of the card can be seen, a lubber line is fitted across the hole below the glass. At centre is a raised dome-shaped cover below which are electrical contacts. Mounted in grey painted aluminium gimbal ring diameter 7.5" (19cm) which is attached to another ring dia. 8.49" (21.5cm) which in turn is attached to the outer grey painted aluminium casing dia. 10.4" (26.5cm) by 69 small springs. A corrector magnet carrier is mounted above bowl being situated at centre of three bowed radial arms attached to rim of outer casing.
Card-Black painted metal card with white markings, graduated to 360 degs.