An ancient gold coin proves that a third century Roman emperor written out of history as a fictional character really did exist, scientists say.
The coin bearing the name of Sponsian and his portrait was found more than 300 years ago in Transylvania, once a far-flung outpost of the Roman empire.
Believed to be a fake, it had been locked away in a museum cupboard.
Now scientists say scratch marks visible under a microscope prove that it was in circulation 2,000 years ago.
Prof Paul Pearson University College London, who led the research, told said he was astonished by the discovery.
The coin at the centre of the story was among a small hoard discovered in 1713.
It was thought to have been a genuine Roman coin until the mid-19th century, when experts suspected that they might have been produced by forgers of the time, because of their crude design.
The final blow came in 1863 when Henry Cohen, the leading coin expert of the time at the Bibliothèque Nationale de France, considered the problem for his great catalogue of Roman coins.
He said that they were not only ‘modern’ fakes, but poorly made and “ridiculously imagined”. Other specialists agreed and to this day Sponsian has been dismissed in scholarly catalogues.
But Prof Pearson suspected otherwise when he saw photographs of the coin while researching for a book about the history of the Roman empire. He could make out scratches on its surface that he thought might have been produced by the coin being in circulation.
He contacted the Hunterian Museum at Glasgow University where the coin had been kept locked away in a cupboard along with three others from the original hoard, and asked if he could work with the researchers there.
They examined all four coins under a powerful microscope and confirmed in the journal, PLOS 1, that there really were scratches, and the patterns were consistent with them being jingled around in purses.
A chemical analysis also showed that the coins had been buried in soil for hundreds of years, according to Jesper Ericsson, who is the museum’s curator of coins and worked with Prof Pearson on the project.