The so-called Louis the Pious imitation solidus was made in or around 816.
It is only the 13th Louis the Pious imitation Solidus found in Britain.
London auctioneers Spink say the coin is ‘a remarkable work of art from ninth century England of exceptional quality and artistic appeal.’ The coin is expected to sell for between £15,000 and £25,000 at Spink in Bloomsbury, London, on Thursday 18th December.
Spink have not revealed the name of the detectorist who found the coin, but they confirm that the coin was found in the West Lindsey district in August.
The Solidus was originally a gold coin issued in the Late Roman Empire. It was introduced in 312 by Constantine 1 and replaced the older Aureus as the main gold denomination.
The imitation Solidus found in the West Lindsey area in August is not the first such coin found in this part of the world.
A spokesperson for Spink said: “Further evidence that Solidi circulated for trade in ninth century Lincolnshire is the discovery in November 1996, near Louth, of a cut quarter of Pious Solidus.”