Ring dial for latitude 51° 30' North. This dial comprises a brass ring with a fixed suspension piece, two figure-of-eight chain links and a suspension ring. On the outer face is a date scale, faintly stamped with the initial letters of each month. The inner face shows an hour scale inscribed on a separate bridging arc, numbered 5-12, 1-7. A sliding central collar allows for adjustment of the sight, which is set into the collar and is moved by means of a buckle-shaped slider.
Johannes Zech is the only maker with initials that would fit those stamped on this dial: 'I Z'. He is known only through another (signed) ring dial, dated 1699 (now in a private collection in Belgium).

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