An extremely rare 12th Century silver penny is expected to fetch more than £10,000 when it is sold, according to auctioneers.
The coin, which depicts King Stephen, was found on the Lincolnshire/South Yorkshire border by metal detectorist Graeme Rushton in 2018.
He did not realise what it was until he showed pictures of it to a museum.
It is believed to be one of only 25 known examples of the coin and will be auctioned in September.
Stephen was a grandson of William I and succeeded his uncle Henry I as king of England in 1135.
However Henry had nominated his only surviving daughter Matilda as his heir and Stephen’s accession plunged England into a 19-year-long civil war, which became known as The Anarchy.
The coin, which depicts Stephen and his wife, also Matilda, was found in a ploughed field just below the surface, Mr Rushton said.
The 50-year-old, from Cumbria, said: “It was only my second visit to the site, which had just been ploughed and flattened.
“I uncovered the coin which at first I didn’t recognise.
“It was only after showing pictures of it to the Fitzwilliam Museum in Cambridge that I realised how significant the discovery was.”
It was found not far from the site of the Battle of Lincoln where Stephen was defeated and captured in 1141 by Matilda’s half-brother, Robert, Earl of Gloucester.
He was later released and in 1153 agreed to accept Matilda’s son Henry as his heir to bring the conflict to an end.
He died the following year.
Auctioneers Dix Noonan Webb said the coin, which was minted in York in the early 1140s, was a fine example from the time.
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