This is the ancient seal of Pilton Priory which dates from about 1420. The seal-making device, also referred to as a seal matrix or die, is held in the Victoria and Albert Museum. On the reverse of a copy held in Pilton Church it says "Copied from the original in South Kensington Museum". The impression shows, on one side, the Virgin Mary between two Angels, and the inscription in Latin "O Holy Virgin to whom I give myself wholly always, intercede for me". On the other side is reported to be an image of the founder of the Priory, King Athelstan (wearing a crown and holding a sceptre) between two trees and shields of arms. It is inscribed, also in Latin, "HOC. ATHELSTANUS. AGO. QUOD. PRESENS. SIGNAT. AMAGO." which means "I, Athelstan, perform that which this present seals". It remains disputed that King Athelstan actually founded Pilton Priory. However, the Prior at the time the seal was made was called Richard Kengeswood, or Kingswood which might explain the rebus of a king between woods.
Thanks to Pilton Church and Margaret Reed for this photograph and information.