Archaeologists have been surprised by the strange finding of ancient Roman coins, buried in the ruins of a castle located in Japan.

The four copper coins were unearthed from the soil beneath Katsuren Castle on Okinawa Island.

They were originally believed to have been a hoax before their true origin was unveiled. Experts have no idea as to how the Roman coins arrived at Uruma, but some believe they might have been traded, with no evidence of a route existing so far.

One archaeologist has said he once thought they were one cent coins dropped by U.S soldiers -the designs that were on the coins were difficult to translate, having been gradually worn away over time.

Though an x-ray examination has revealed many of the relics have the image of the Emperor Constantine I, another coin pictured a soldier wielding a spear.

Uruma’s Board of Education has noted that Okinawa’s trade with China and Southeast Asia was flourishing during the castle’s existence.

It is believed that these precious historical objects are proof of a trade link between Okinawa and the Western world.

Since the unearthing on the site started in 2013, researchers have also discovered six other coins that may date back to the Ottoman Empire. The Roman coins seem to be a lot older; they go back to around 400 AD, according to the estimates.

The board of education located in the Japanese city of Uruma had announced the finding and they said the story of how the coins came to Japan is still buried in doubt.

The Kastsuren Castle was noted to have been the focal point of trading partnerships with Asian countries and China, yet ties to Europe had not been evident up until the recovery of the coins.

The ruins of the castle were documented in the year of 2000, and it was on the World Heritage list as part of the Gusuku Sites and the Related Properties of the Kingdom of Ryukyu.

Education spokesman Masaki Tokou told CNN: “It is a strange and interesting find.

We don’t think that there is a direct link between the Roman Empire and Katsuren Castle, but the discovery confirms how this region had trade relations with the rest of Asia.”

The coins are going to be examined further, and will be displayed at the Uruma City museum in Okinawa up until the end of November.

Since 2013 a squad of archaeologists from Uruma’s local Board of Education has been unearthing Katsuren Castle. This is a UNESCO world heritage location in the southernmost prefecture.

The ancient coins, ten in total, had only been recently found when Toshio Tsukamoto, a researcher from Gangoji cultural properties department, spotted them as he traveled to the castle from Nara.

Some other artifacts that have been discovered at the Katsuren castle’s digging site include Japanese ceramics and objects that had been used by the castle inhabitants.

We have another story on Roman Coins, check it out:Unearthed 1,300 pounds – half a ton- of Roman coins

Other finds include Chinese coins and ceramics that could have been acquired through trade, and date back at least 600 to 700 years.

They are going to analyze these objects together with the other coins to find out how they might have ended up at the castle.