Bowl- Brass bowl painted black and glazed top and bottom. There is a filler hole on the side and four expansion chambers also on side. A diameter bar at the base of the bowl supports the pivot arrangement. A black lubber spike projects horizontally from the inner side of the bowl. The bowl has gimbal sprockets on the side.
Card- A transparent card with a painted black and white centre, with the white markings showing 16 points. The transparent rim is graduated quadrantally in degrees. The card is 4.5" (11.4cm) dia. and is attached to the float by a wire framework.
Needle- Two needles in tubular holders are attached to the wire framework beneath the card 3" approx in length.