A UNIQUE and unpublished coin from the reign of David I of Scotland that was minted in Carlisle is set to fetch a large sum of money at auction this week.

The coin which is believed to have been minted around the mid 1100s is estimated to fetch around £15,000-20,000 when it goes up for sale on Thursday by auctioneer Noonans Mayfair.

The silver penny was discovered in Carlisle near a medieval fort where it minted coins for Henry I and Stephen of Blois following the discovery of a silver deposit in the 1120s.

According to the coin specialist Jim Brown, what makes the discovery of the silver penny so historically important is the unique nature of the design.

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It features the same moneyers, an individual who is officially permitted to mint money, as the Henry I and Stephen of Blois coins which were Erembald, Udard and Wilealme.

However, some of the David I of Scotland pennies also featured the Edinburgh mint signature as experts believe it could have been a commemorative coin to celebrate the fortification of the Carlisle fort after the Scots took it over in 1136.

Jim Brown explained the discovery of the David I of Scotland coin is its unique design which departed from the “norm” of the period.

He said: “This is a find of considerable historical and numismatic importance. It is not really surprising that new varieties of medieval coins turn up from time to time - this is to be expected.

(Image: Noonans Mayfair)

“What makes this find so different is the unique nature of the design - a complete and totally unexpected departure from the norm.”

He continued: “The original medieval fortress at Carlisle that was constructed in 1092, after the capture of the city from the Scots by William Rufus. Some 30 years later, Henry I decreed it be rebuilt in stone and ‘fortified with a castle and towers’.

“This is probably the medieval keep that can be seen today, albeit much altered in the interim.”

(Image: Noonans Mayfair)

Henry I died in France in 1135 and a period of unrest played out around the disputed succession to the throne between Henry’s daughter Matilda and her cousin Stephen of Blois.

Stephen, on hearing of Henry’s death, was quicker than Matilda in returning to England staking his claim and was crowned in Westminster Abbey three weeks later.

Within days of Srephen’s crowing, David I of Scotland began an invasion of the north of England, believed due to the support of Matilda who was his niece.

Carlisle fell to the Scots before in 1136 and possession was ratified by the first Treaty of Durham a few months later.

David was quick to continue the fortification of the castle begun by Henry a decade earlier.

Brown added: “The exact occasion of its striking however can only be surmised. It was a tumultuous period of alliances, battles and treaties changing with the ebb and flow of the political and military struggle.

“In view of the obverse type, it may be to commemorate David’s fortification of his new power base in Cumbria - an issue unparalleled in British medieval numismatics.”