A gold half-noble of Henry VI, struck 1422-1427, has been found in a field just outside Boston.
The coin was folded over which was a common practice in medieval England, often done to mark a vow, such as an engagement.
It was found and recorded as part of the British Museum’s Portable Antiquities scheme, supported by Lincolnshire County Council.
About 52,000 objects have been reported in Lincolnshire since the scheme started in 1997.
The oldest is a flint axe from the Lower Palaeolithic period and provides the oldest evidence of human life in the county.