Bowl- Black painted brass, filler plug at side, glazed bottom incorporates an expansion chamber. Inside of bowl silvered, fitted with a black lubber line which can be moved against a graduated scale. Verge ring is graduated to 360 degs. The verge glass has a knob at the centre which, when depressed, locks the card. mounted in rubber shock absorbers and can be turned against a scale to correct co-efficient a. A cover plate at bottom has a plate with directions for swinging and is fitted with four lamps. Inside cover are other corrector magnets.
Pivot- Double pivots; the upper pivot is attached to knob ,mounted at centre of verge glass. The lower pivot is attached to centre of bottom of bowl. Both consist of a steel stump with sharpened points.