Diptych dial for latitude 49° North. This square, ivory dial consists of two leaves that fold flat when not in use. Leaf Ia contains a combined nocturnal and universal equinoctial dial surrounded by a compass rose showing 32 points with a fleur-de-lys for North. On leaf Ib is a universal equinoctial dial inside of which is a silver lunar volvelle. The remainder of the leaf is decorated with a view of a harbour, possibly Dieppe, and ships and dolphins.

A compass, covered by a (broken) mica plate and encircled by hours for a horizontal dial, is set into leaf IIa. Red string for use with the horizontal dial (for latitude 48°) is attached between the inner surfaces of the two leaves. On leaf IIb is an altitude quadrant with a shadow square. Inside this is a vignette of a storm-driven ship and the remainder of the leaf is engraved with grotesques and mythical beasts. The leaves are held together by two silver hook fasteners. Engraved on the hinge end of the upper leaf is the maker's signature: 'Dauid Asselinne A Dieppe'.

This is one of few surviving instruments by Asselinne, whose instruments, as in this example, are characterised by high quality engraving. It is almost more of a compendium than a diptych dial, carrying a nocturnal, quadrant, lunar volvelle, equinoctial dial and horizontal dial. It has a square wooden box with brass fittings and a green baize lining.

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