They were searching for an old infirmary. What they uncovered was an "exceptional and extremely rare treasure": 2,200 silver coins, 21 gold coins, a gold signet ring, gold foil, and a circular object also made of gold.
It's a collection unlike any ever found, according to French archaeologists, who made the discovery together with students from the University of Lyon, per a release.
For the past two years, Lyon students have participated in digs at the Abbey of Cluny in Saone-et-Loire, among the largest monasteries in Western Europe in medieval times.
But the most recent class was especially lucky. Over a monthlong dig that wrapped up in late October, they uncovered what researchers say is the largest collection of French denier coins ever found.
The team had been trying to find the corner of the infirmary when coins suddenly spilled from a buried cloth bag. "I thought how I'd never again see something like it in my life as an archaeologist," a student tells the Local.
The deniers are believed to mostly have been minted at Cluny some 900 years ago when the coins were the prevailing currency. But they were surprisingly found next to a hide bundle housing Islamic gold dinars minted in Spain and Morocco around the same time.
The ring inscribed with a religious greeting and depicting the bust of a god was also in the bundle, say researchers. An expert notes the owner of the items could've exchanged them for "between three and eight horses" in the Middle Ages—if they'd been retrieved.
(The first US coin may have been found.)
This article originally appeared on Newser: Searching for a Foundation, They Found Treasure Instead