Archaeologists discovered ancient gold coins in an unexpected location during a recent excavation in Bulgaria.

The five Byzantine coins, which date back to the reign of Justinian the Great, were uncovered by archaeologists digging at a site in the northern Bulgarian village of Debnevo. The excavation was announced by Dr. Stiliyan Ivanov, an associate professor at the National Institute of Archaeology and Museum, on Aug. 27.

The village, which is close to a fifth-century fortress, has been the site of excavation projects for the past five years. But researchers were stumped when they found the coins in the remains of a 10th-century house.

As Justinian had ruled the Byzantine Empire from 527 to 565 A.D., the currency predated the structure by more than 400 years.

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Ivanov told Live Science that medieval builders likely found the coins while they were constructing the 10th-century house. The house burned down later that century, and archaeologists believe the site was abandoned soon after.

The coins would still have been considered valuable in the 10th century, and the medieval residents likely kept them as heirlooms. Ivanov told Fox News Digital that he's "very glad" about the interest in the coins.

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Three of the coins are in excellent condition while two others are stuck together. Archaeologists believe that they likely melted in the fire that destroyed the medieval dwelling.

Justinian's face is visible in the center of the coins, as is the inscription "Our Lord Justinian Perpetual Augustus." The phrase "Victory of the Augusts" is inscribed on the back of the artifacts.

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In addition to the coins, archaeologists also discovered axes, sickles and ceramic vessels, in addition to bronze rings. But the coins were the most eyebrow-raising discovery of the excavation.

The dig is one of multiple excavations that led archaeologists to ancient coins this summer. In August, researchers found ancient Greek gold coins in modern-day western Turkey.

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In May, a woman stumbled upon 2,150 silver coins minted between 1085 and 1107 during a walk in the Czech Republic.

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