Diptych dial for latitude 50° North. This is a rectangular ivory dial consisting of two leaves that fold flat when not in use. Leaf Ia features a standard windrose (see related terms). Leaf Ib is as standard except there is no dial for daylight hours. The vertical dial is decorated with a large blue six-pointed star/flower motif in a double circle. Leaf IIa is as standard except the hour scale is numbered in black and the compass is offset 11° West of North to allow for magnetic variation. The blued needle (probably a French replacement) has an open ring indicating South. At the centre of the compass is the maker's mark of Leonhard Andreas Karner - a hand. There is also a faint incomplete hand mark on leaf IIb.

There is a single horizontal dial for Italian and Babylonian hours; Italian hours in red, Babylonian in black, and the pin gnomon is missing. There is a replacement string gnomon. On leaf IIb, Karner's makers mark appears again to the right of the gnomon hole and it is signed 'LAK 1733'. The leaves have brass hook fasteners. A tapered ivory pointer is held in a slot in the right hand side of the lower leaf; much of the slot has broken away. On the lower leaf there is also a crack.

This is a rare full-size diptych by Leonhard Andreas Karner, who seems to have specialised in the sort of miniature diptychs produced in large quantities by the Karner workshop in the 18th century. It is a relatively simple dial constructed for a single latitude.

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