Diptych dial for latitude 49° North. Rectangular wooden dial consisting of two leaves that fold flat when not in use. Leaf Ia is blank. Leaf Ib displays a vertical dial with hour-lines in red radiating from a double semicircle. Leaf IIa contains the compass with the hours for the horizontal dial set around it. Hour-lines radiate from the string gnomon, which is red and attached between the inner surfaces of the two leaves. The compass is marked with the cardinal points in Latin and is offset 16° West of North to allow for magnetic variation. The needle is blued, in the form of an arrow, and surmounted by a brass pyramidal pivot. The glass plate is held in place by a copper ring.

In the compass bowl are two maker's marks: a fleur-de-lys on the right hand side and a 'B' on the left hand side. A brass pin for keeping the leaves aligned when closed is on the bottom right hand side. Leaf IIb is bare. The leaves have brass hooks for holding the dial open.

Like AST0291, the fleur-de-lys that appears in the compass bowl might suggest Lienhart Miller as a maker, but the 'B', which is also set in the compass bowl, possibly indicates the Karner workshop. A similar dial in the British Museum (registration no. CAI.2417) has a hole for a plumb bob (still present) and a crown as well as the fleur-de-lys in the compass bowl. Another is in the MHS, Oxford (new inventory no. 52562).

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