A rare 1,200-year-old silver coin featuring a portrait of the emperor Charlemagne was recently rediscovered and taken on a wild journey from a farm in France to the bidding grounds of eBay.

A man in France wanted to build a house but was short of cash. He remembered that his grandfather had a collection of coins. After going through his grandfather's collection, the man discovered a coin that was known as a denarius and put it up for auction on eBay.

The director of the Route, a group of municipal museums in Aachen, Germany, that focus on cultural history, said that one of their experts checks eBay for archaeology.

The museum entered a bid. They got the coin depicting Charlemagne and his imperial title: IMP(erator) AVG(ustus), a reference to Emperor Augustus, the first Roman emperor and a title used by the many emperors of the Roman Empire. He wouldn't reveal the coin's price, but he did say that it was not that expensive. We are very content.

The gold treasure was found during the fall of the Roman Empire.

After the fall of the Western Roman Empire in the fifth century A.D., Charles the Great became the first ruler to unite Western and Central Europe.

The coin portrait depicts Charlemagne as a Roman emperor, which is quite unusual for a Frankish king. He is dressed like a Roman general.

The portrait shows a round face, a mustache and a short neck, which was noted by Einhard, according to Pohle.

He put his portrait on the 0.7-inch-diameter (1.9 centimeters) coin, which is a good copy of what the Roman emperors did in their times.

Most of the denarii coins have his name on them, but no portrait, according to Marjanko Pileki, a numismatist and research assistant.

The back of the coin has a Christian cross on it, and it looks like a church and a temple.

The back of the coin features a mix between a Roman temple and a church.

The back of the coin features a mix between a Roman temple and a church. (Image credit: Stadt Aachen/Route Charlemagne)

When was it minted?

The experts at the museum have determined that the coin was likely made in the city of Aachen, where Charlemagne was born and later died. The date of its minting is not known. He didn't immediately use the title "Emperor Augustus" after being crowned Roman emperor.

Although he was crowned in 800, he didn't use the title until after 800. The title was used by Charlemagne instead.

According to Pileki, the Byzantine Empire recognized the emperorship of Charlemagne in 822 and he started using the title on the coin. Louis the Pious was appointed co-emperor and had similar coinage made.

Charlemagne was gravely ill for the last three to four years of his life and worried about the future of the empire. The portrait coinage were created in the last year of his life. At a time when he was probably trying to make an orderly succession.

The coins were intended to commemorate the occasion of the emperor's coronation and therefore did not really serve as money like the other denarii of Charlemagne, which do exist in significantly larger numbers without a portrait and imperial title.

It is difficult to say how much this coin was worth at the time.

It was originally published on Live Science.