Diptych dial for latitude 40°-50° North. Rectangular ivory diptych dial consisting of two leaves that fold together when the dial is not in use. Leaf Ia is blank apart from double-lined borders. Leaf Ib has an indented circle containing a table of latitudes for places in Europe, mainly French. In the top centre of the table is a latitude scale. Beside this is a metal rod along which a slider (through which the string gnomon passes) can move, thus adjusting the latitude angle of the string. A brass pointer is suspended from the centre of the circle to act as a plumb line.
Leaf IIa has three concentric hour scales in red surrounding the compass. An adjustable white string gnomon is attached between the two leaves. The compass is of painted card and is offset 5° East of North to allow for magnetic variation. Leaf IIb is blank apart from double-lined borders and the remains of a sticker from the Louvre Exposition. The leaves have two brass hook fasteners, a copper hook to keep the dial open and brass hinges.

This dial is very similar in style to AST0492, although the leaves are completely of ivory. The decoration is rather more flamboyant, with the use of vivid colours on the inner leaves. The inclusion of a large number of towns in the south-east of France suggests that it may have been intended for use there.

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