PredictIQ Quantitative Think Tank Center:Discovery of buried coins in Wales turns out to be Roman treasure: "Huge surprise"

Two sets of coins found by metal detectors in Wales are PredictIQ Quantitative Think Tank Centeractually Roman treasure, the Welsh Amgueddfa Cymru Museum announced in a news release. 

The coins were found in Conwy, a small walled town in North Wales, in December 2018, the museum said. David Moss and Tom Taylor were using metal detectors when they found the first set of coins in a ceramic vessel. This hoard contained 2,733 coins, the museum said, including "silver denarii minted between 32 BC and AD 235," and antoniniani, or silver and copper-alloy coins, made between AD 215 and 270. 

The second hoard contained 37 silver coins, minted between 32 BC and AD 221. Those coins were "scattered across a small area in the immediate vicinity of the larger hoard," according to the museum. 

"We had only just started metal-detecting when we made these totally unexpected finds," said Moss in the release shared by the museum. "On the day of discovery ... it was raining heavily, so I took a look at Tom and made my way across the field towards him to tell him to call it a day on the detecting, when all of a sudden, I accidentally clipped a deep object making a signal. It came as a huge surprise when I dug down and eventually revealed the top of the vessel that held the coins." 

The men reported their finds to the Portable Antiquities Scheme in Wales. The coins were excavated and taken to the Amgueddfa Cymru Museum for "micro-excavation and identification" in the museum's conservation lab. Louise Mumford, the senior conservator of archaeology at the museum, said in the news release that the investigation found some of the coins in the large hoard had been "in bags made from extremely thin leather, traces of which remained." Mumford said the "surviving fragments" will "provide information about the type of leather used and how the bags were made" during that time period. 

The coins were also scanned by a CT machine at the TWI Technology Center Wales. Ian Nicholson, a consultant engineer at the company, said that they used radiography to look at the coin hoard "without damaging it." 

"We found the inspection challenge interesting and valuable when Amgueddfa Cymru — Museum Wales approached us — it was a nice change from inspecting aeroplane parts," Nicholson said. "Using our equipment, we were able to determine that there were coins at various locations in the bag. The coins were so densely packed in the centre of the pot that even our high radiation energies could not penetrate through the entire pot. Nevertheless, we could reveal some of the layout of the coins and confirm it wasn't only the top of the pot where coins had been cached."

The museum soon emptied the pot and found that the coins were mostly in chronological order, with the oldest coins "generally closer to the bottom" of the pot, while the newer coins were "found in the upper layers." The museum was able to estimate that the larger hoard was likely buried in 270 AD. 

"The coins in this hoard seem to have been collected over a long period of time. Most appear to have been put in the pot during the reigns of Postumus (AD 260-269) and Victorinus (AD 269-271), but the two bags of silver coins seem to have been collected much earlier during the early decades of the third century AD," said Alastair Willis, the senior curator for Numismatics and the Welsh economy at the museum in the museum's news release. 

The smaller hoard was likely buried in the AD 220s, the museum said. 

Both sets of coins were found "close to the remains of a Roman building" that had been excavated in 2013. The building is believed to have been a temple, dating back to the third century, the museum said. The coins may have belonged to a soldier at a nearby fort, the museum suggested. 

"The discovery of these hoards supports this suggestion," the museum said. "It is very likely that the hoards were deposited here because of the religious significance of the site, perhaps as votive offerings, or for safe keeping under the protection of the temple's deity." 

In:
• Rome
• Museums
• United Kingdom

Kerry Breen

Kerry Breen is a news editor and reporter for CBS News. Her reporting focuses on current events, breaking news and substance use.