Diptych dial for latitude 50° North. Rectangular ivory dial consisting of two leaves that fold flat when not in use. Leaf Ia carries a standard lunar volvelle (see related terms), except both hour scales are numbered clockwise and the brass disc is not scalloped. Leaf Ib has a vertical dial and displays star motifs in red and black. A black string gnomon, for use with this dial, is attached between the inner surfaces of the two leaves. Inscribed at the top of the leaf are the words 'SOLI DEO GLORIA' (Glory to God alone).

Leaf IIa is as standard except there is no horizontal dial. Surrounding the compass, whose cardinal points are named by Latin initials, is a series of concentric engraved and coloured circles. There is also a single dial for Italian hours only. The leaf carries the signature, 'IORG MILLER'. Leaf IIb is bare apart from the maker's mark (S), which appears twice. It has a yellowed surface. The leaves are held together by brass hook fasteners (one missing) and there is a single brass hook for holding the dial open. The hinges are also of brass.

Dials by Jörg Miller are very rare. There are none in the Lewis Evans collection at Oxford, in the British Museum or in the Harvard collection. E. Zinner (1956) records only this example of his work. Unlike most diptychs, this one has no horizontal dial apart from one for Italian hours. The main dial is the vertical dial on leaf Ib.

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