It is the size of a fingernail with battered edges to match.But this silver coin, discovered in a field, could be worth up to £80,000 if proved to be a genuine Roman antique.

Colin Popplewell, 58, and Mark Hildreth, 38, say the coin - which is the size and weight of a penny - is only the second one in history to be found featuring the short-lived Emperor Proculus.

A metal detecting expert, Julian Evan-Hart, certainly believes the coin is genuine and that it was minted to mark the brief rise to power of Proculus in 280AD.

Father-of-two Mr Popplewell, who made the find in a field near Stamford Bridge, East Yorkshire, on November 7, said: 'The first coin with Proculus was found in a collection in Germany in the 1980s. It sold in 1991 for £40,000.

'It was in a private collection that dated back a century so there was no way of validating whether the coin was authentic or a contemporary forgery, made in the Roman times.

'Our find is ground-breaking because it validates the first coin and gives weight to the history of Proculus - it really will change the history books.'

But coin specialist and renowned academic Roger Bland, who is Keeper of the Prehistory and Europe Department of the British Museum, disagrees that the coin is genuine.'

He said: 'I don't believe any coins of Proculus were ever made and this one is probably a 15th century forgery.

'The only source for our knowledge of him is a controversial history book, written at the end of the 4th century AD, much of which was made up.

'This coin has been made from the same dye, or mould, as another in the Munich Museum, which is widely believed to be fake.

To read the complete article, see:History-changing coin or a 15C forgery? Debate over 'Roman' artefact found in field by metal-detecting friends(www.dailymail.co.uk/news/article-2233959/Debate-Roman-artefact
-coin-Proculus-field-metal-detecting-friends.html)