Auctioneers hope historic silver fragment will make golden sum

The coin is one of only a handful of examples which have survived the intervening 365 years since they were issued in North Yorkshire.

The emergency issue five-shilling piece was found by a metal detectorist in Lincolnshire, who did not realise its significance until one of his friends pointed out the Scarborough Castle stamp.

It is thought the coin was kept as a Civil War keepsake as it is especially worn – indicating it could have stayed in someone's pocket for many years.

The silver coin has been given an estimate of between 7,000 and 9,000.

However it is expected to attract international interest and the auctioneers in London hope the price could be much higher.

Chris Wren, the managing director of TimeLine Auctions said: "Unlike other countries, the only time we really see siege money being used in England is during the Civil War period.

"These pieces do have a certain mystique and we are hoping for a lot of interest."

The coin was used by Royalist officer to pay one of his troops as the castle came under attack from Oliver Cromwell's Roundheads in 1645.

Silver plates and other ornaments were broken up and used as emergency currency to persuade the under-siege Royalist troops not to surrender or revolt.

Each cut piece was stamped with its bullion value and an image of the castle.