Magnetic dial for latitude 51° North. The dial is printed on a white compass card on the underside of which is a bar magnet, set on a point, to orient the dial correctly. Around the edge of the card is an evenly divided circle of hours, numbered clockwise 1-12, 1-12. This is marked 'NIGHT, MORN, NOON, EVEN' at the appropriate points. Within this is the hour ring of the dial, numbered clockwise IIII-XII, I-VIII. Four compass points are shown in the centre with North marked by a fleur-de-lys, the others by English initials. It has a simple copper gnomon. On the edge of the box is a fixed ring of towns and other geographical features around the world, supplied to allow the calculation of the time in other countries including London, Bombay, Botany Bay, Mexico, Jamaica and Iceland. There is a domed glass cover over the whole instrument and it is set in a round wooden case with a push-fit lid.

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