This is an early English "Scientific" Sundial, with exactly calculated, unequal hour angles. Early sundials of this type are rare. It was excavated at Scadbury Manor, home of the Walsingham family, by Orpington & District Archaeological Society.
It was never completed; it has a finely-finished surface but only some of the morning and afternoon numerals are present (it shows 8am to 4pm) and it had been deliberately broken in two. It may have been a practise piece ? the angles do not correspond exactly to those for Chislehurst, but it would be correct for somewhere further north. Maybe an apprentice made it. Time was shown from the shadow cast by a metal pin.
At this date, accurate scientific dials were prestige items for the aristocracy. The Walsinghams were an important political dynasty - they had connections with the Tudor court. Sir Edmund Walsingham (1480-1550, around the same time as the sundial) was Henry VIII's Lieutenant of the Tower of London, responsible for his prisoners, such as Thomas More, Thomas Cromwell and Anne Boleyn. Sir Francis Walsingham was Elizabeth I's Secretary of State. Sir Thomas Walsingham IV was a patron of the playwright Christopher Marlowe