Diptych dial for latitude 49° North. This octagonal ivory dial consists of two leaves that fold together when not in use. Leaf Ia is blank apart from typical Dieppe 'pecked' ornamentation in the border. Leaf Ib displays an equinoctial dial and a lunar volvelle. The pin gnomon for the equinoctial dial is missing. Leaf IIa has a horizontal dial set around the compass. The green string gnomon for use with the dial is broken. A printed and painted compass card is marked with a horizontal projection with a date and zodiac scale. The compass needle is blued, forked at its South end and surmounted by a brass pyramidal pivot. Leaf IIb is blank apart from a border, as on leaf Ia. The leaves have two silver hook fasteners, a silver hook to hold the dial open and silver hinges.

Although the Dieppe sundial makers are best known for their magnetic azimuth dials, a number of ordinary diptych dials were also produced. The horizontal projection in the compass bowl can be used to tell the time. If the dial is rotated until the shadow of the string gnomon falls on the meridian line of the horizontal dial, the compass needle will point to the time on the line of the sun's declination corresponding to the date. This dial would only have been accurate during the 1660s and 1670s when there was very little or no magnetic variation in France.

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