Diptych dial for latitude 49° North. This miniature oval shaped dial consists of two leaves that fold flat when not in use. The lower leaf is wooden and covered with ivory and the upper leaf is made of ivory alone. Leaf Ia is blank. Leaf Ib features a vertical dial with hour-lines radiating out from the string gnomon. Leaf IIa has a compass with the hours for the horizontal dial set around it. A string gnomon is attached between the inner surfaces of the two leaves. The compass is marked with the cardinal points in Latin and is offset 6° East of North to allow for magnetic variation. Miller's makers mark - a Fleur-de-lys - appears upside-down on the left hand side of the compass. There is a brass pin at the bottom right for keeping the leaves aligned when closed. Leaf IIb is blank apart from the maker's mark stamped at the non-hinge end. The leaves have a brass hook fastener, a brass hook for holding dial open and a brass carrying loop.

The use of a mixture of wood and ivory for the miniature diptych dials became common during the 17th century, eventually being replaced with wood alone at some point during the 18th century. This is a very simple instrument with a minimum of engraving and only the main vertical and horizontal dials included.

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