The Estendard du Château (standard of the castle), an unlidded brass vessel used as the standard Jersey cabot measurement until the late 20th century, was believed until recently to date from the late 17th or early 18th centuries.
Investigations into the history of Mont Orgueil have revealed that the estendard is far older, having been made in 1330.
The plain pot was in use by Weights and Measures until the 1960s.
When its useful life was over it was put into storage and forgotten about while historians and archaeologists searched for it.
