Divers in Italy have discovered tens of thousands of fourth-century bronze coins off the coast of Sardinia.
Authorities initially received a tip from a diver who had spotted something shiny near the Mediterranean island’s northeastern shore, according to the Associated Press. They didn’t specify when this sighting took place.
Soon after, officials sent a team of divers to scope out the scene, which is located near the town of Arzachena. Some of the divers were affiliated with an art protection squad, while others were connected to the ministry’s underwater archaeology department.
Beneath the waves, they found the ancient coins—known as follis—poking up from the seafloor. A video shared by Italy’s culture ministry shows divers using an underwater metal detector to locate the artifacts, gently brushing away sand with their hands. After extracting the coins, they placed them in large red bins, which they then hauled to the surface.
The exact number of coins recovered is unclear, though officials estimate it’s likely between 30,000 and 50,000, based on the objects’ weight. All of the coins are in an “exceptional and rare” state of conservation, according to a translated statement from the culture ministry. Only four are damaged, and even those feature inscriptions that are “still legible.”
Experts also found many amphorae, a type of jug with a slender neck and two handles. They think some of the amphorae were made in Africa, while others were made in Asia.
Archaeologists found the treasure trove in a large, sandy area between the beach and the underwater seagrass. Because of the shape and positioning of the seabed, they say a shipwreck could be concealed nearby.
Based on the markings on the coins, the team thinks they date to between 324 and 340 C.E. Some of the objects depict Constantine I, who was the Roman emperor from 306 to 337 C.E.
The recovered coins come from mints located across the Roman Empire, per CNN’s Hafsa Khalil and Sharon Braithwaite.
Looking ahead, the team plans to restore and study the coins in the hope of learning more about their origins. Already, they are “one of the most important discoveries of numismatic finds in recent years,” says Luigi La Rocca, who leads the regional government archaeology division, in the statement.
The coins also highlight the “richness and importance of the archaeological heritage that the depths of our seas, crossed by men and goods since the most ancient times, still guards and conserves,” he adds.