Card- Mica covered with paper, white with black markings, graduated to 1/4 points. At centre of card is a hole 1.15" dia. to accommodate pivot.
Needle- Four light edge bar needles each composed of two laminations of steel 2 x 3.5" and 2 x 2" long, 0.25" deep, each 1" apart. Attached to a light metal ring 3.5" dia. which is screwed to card.
Pivot- Inverted type (missing) carried in double gimbals. Only one being present, secured by brass brackets to inner needles.