Diptych dial for 49° North. Rectangular ivory dial consisting of two leaves that fold flat when not in use. All the markings are in black. Leaf Ia contains an equinoctial dial with an hour-circle for use in the spring and summer months and a central polar dial. There is a central metal rivet with a hole for the pin gnomon (missing). Leaf Ib displays a lunar volvelle and the southern part of the equinoctial dial. On its right-hand side is a latitude scale for use with the equinoctial dial. Leaf IIa has a compass with the hours for the horizontal dial set around it.

On the compass's printed paper insert, the cardinal points are marked in Latin and four winds are depicted as human heads at the quadrantal points. On the right-hand side is a slot for the accommodation of a brass strut for use with the equinoctial dial. A string gnomon is attached between the inner surfaces of the two leaves. Leaf IIb has a double and single-lined border. The leaves have brass hook fasteners, which are broken, and brass hinges.

The compass card is similar to those found in Nuremberg diptych dials. However, the style of decoration on the dial is typical of that appearing on dials made in Dieppe in the second half of the 17th century. It is probable that the compass card was added to a French instrument at a later date, and was made to resemble the Nuremberg compasses.

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