Magnetic dial for latitude 51° North. It has a paper dial card with an outer circle of 32 compass points; North indicated by a fleur-de-lys. The hour ring is divided clockwise with a sunface at the South point, and a simple brass gnomon is set on the dial-plate. A glass plate is set over all and is held in place by the metal of the case. A magnetic bar attached to the underside of the card orientates the dial correctly and it is set for a magnetic variation of 19° West of North. The dial has a round wooden case with a domed top, brass hinge and hook fastener.

In the lid of the box is a table of corrections for the equation of time. Printed in the centre of the table is the legend 'FAST MEANS THAT THE CLOCK SHOULD BE FASTER THAN THE DIAL. SLOW, SLOWER.'. While the dial-plate/ compass card is similar to other magnetic dials, the highly domed case and the inclusion of the equation of time are unusual, as the small dial-plate hinders the reading of adjustments to mean time. Since the dial was set for a permanent magnetic variation, the dial would only have been useful shortly after the time of production and would not now be of practical value.

For more information regarding this dial please refer to the OUP & NMM catalogue, 'Sundials at Greenwich'.