But it is not the first time the ring has supposedly returned to France, says Olivier Bouzy, head of the Joan of Arc archives in the north-central French town of Orleans.

In the 1950s, a French-English doctor called James Hasson said he had bought the ring and presented it around France. Experts at the time cast doubt on its authenticity, says Bouzy.

Part of the problem is the number of copies in circulation. There was even a tombola in the early 20th century in which prizes included versions of the ring.

"Around Joan of Arc, we already have several cases of false objects," says Bouzy.

One of the more famous was when a fragment of an Egyptian mummy was mistaken for one of Joan of Arc's ribs, recovered from the stake.

The Museum to Joan of Arc in Rouen chose not to participate in last month's auction, fearing another fake.

But medieval historian Philippe Contamine, while not yet convinced, says he had not given up all hope.

"It's unlikely - there are too many unknowns," he says. "But unlikely can still turn out to be real."