Bowl-Brass, with large lead balancing weight fited to base. Fitted with card stop-mechanism, working through pivot, operating on rim of card and card lifting mechanism operated by lever at side of bowl. Verge glass has cross thread lines mounted on underside. Brass verge ring is fitted with two folding sight vanes. Fore sight, height 4.2" (10.6cm) is open frame sight with a thread and black glass reflector. Back sight has a slit and carries a sliding frame with a dark glass filter. Verge ring rotates through 360 degrees. Interior of bowl painted black and fitted with brass strip, incorporating stop mechanism which carries lubber line. Fitted with brass gimbal ring, dia. 9.5" (24.1cm).
Card-Mica, covered with green paper. Graduated to 32 points and quadrantally in degrees. Edge of card carries a silvered brass ring graduated in degrees to 360. Black lettering on green ground with decorative North point. Jewelled pivot cap fitted to centre of card.
Needle-Two parallel edge bar needles, length 6.2" (15.7cm), depth 0.5" (1.3cm) connected by two metal straps screwed to underside of card.
Pivot-Steel pin mounted in brass stem secured to base of bowl engages in pivot cap.