TWO metal detectorists say a Roman coin they have found in a field near Stamford Bridge could net them at least £60,000 – and will change the world’s understanding of Roman history.

Colin Popplewell and Mark Hildreth say the silver coin is only the second one ever to be found featuring the “usurper” Emperor Proculus.

They said coin experts around the globe are hugely excited by the discovery, and an auction house which is coming to York today to examine the coin has said it could fetch between £60,000 and £80,000.

“We’ve been metal detecting for 30 years and it’s the find of a lifetime,” said Colin, from the Wigginton Road area of York, who was out detecting with Mark in the area of a former Roman road earlier this month when he discovered the coin.

He said while he did not recognise the emperor’s features, he did not initially realise its rarity or value. He and Mark photographed the coin out in the field and put the image on a Facebook site used by metal detectorists.

Julian Evan-Hart, a metal detecting expert, investigated and told them it was a coin minted to mark the brief rise to power of Proculus in 280AD.

Mark, from the Hallfield Road area, said they would give a proportion of the proceeds to the farmer who owns the field and gave them permission to go detecting, and then share the remainder between them 50/50, as they had always agreed. He said a single coin was not considered treasure trove and therefore did not need to go to an inquest.

Mr Evan-Hart said: “Colin has made an astounding contribution to world numismatics by this find of a single debased silver coin. It is true history will now have to be re-written as there are now two coins of Proculus in the world – and how great is that?”

“Proculus is no longer the subject of a single known coin, we now now that he had coinage. Although we suspected it before, it is now fact.

Christopher Webb, of specialist auctioneers and valuers of coins, Dix Noonan Webb, said it was an “extremely rare and valuable coin, possibly the second known.” He said at auction, it could fetch up to £50,000, but this estimate was later raised to between £60,000 and £80,000.

Proculus facts

PROCULUS was a Roman usurper who challenged Emperor Probus’s right to be emperor in 280.

An ambitious soldier, he proclaimed himself joint emperor with Bonosus at the invitation of the people of Lugdunum (Lyon), who had started a rebellion against Emperor Probus. On Probus’ return from fighting in Syria, he forced Proculus to retreat north. Proculus was eventually handed over to Probus, who had him killed in 281.