Recovered Gold Ring, believed to be 9th-10th century Anglo-Saxon (photograph courtesy of the British Museum/ Mercia Police Department)

Two British metal detectorists, George Powell and Layton Davies, have been sentenced to serve jail time after concealing their discovery of a trove of Viking coins on farmland in Herefordshire near the English-Welsh border in 2015, now worth an estimated $15.4 million. The collection, which also includes jewelry and ingots, is believed to be Anglo-Saxon items buried by Vikings around 878 or 879 CE, and remained concealed until the police received a tip-off by other members of the metal detecting community and the British Museum. Powell, Davies, and the coin dealers Simon Wicks and Paul Wells, who assisted in selling the concealed find, have all been sentenced to serve up to 10 years in jail.

Recovered items, believed to be 9th-10th century Anglo-Saxon (photograph courtesy of the British Museum/Mercia Police Department)

Viking era specialist and curator of early medieval coins at the British Museum Gareth Williams, told the BBC that “Britain has the most generous system in the world for rewarding finders when they follow the law,” which allows detectorists 14 days to report the discovery. Under Britain’s Treasure Act, a market-value reward is usually split between the finders and the landowner. The 30 or so coins that have been recovered are believed to be only a fraction of a larger hoard of around 300, revealed in photographs on Davies’s phone. Despite a yearlong investigation, the entire collection has yet to be found. Detective Constable Nigel Cleeton, an investigating officer for the operation, said, “In all my policing years of service this is the most unusual investigation I have been involved in.”

Recovered Anglo-Saxon “Two Emperor” coins (photograph courtesy of the British Museum/Mercia Police Department)

The historical importance of the find comes at a “key moment in the unification of England” Williams explains, and 5 of the 31 coins depict King Alfred the Great of Wessex and a lesser-known monarch, Ceolwulf II of Mercia, sitting together, revealing a previously unheard of alliance. The potential to change current understanding of early English history at a critical time makes the lost items all the more important to find. Other recovered items, now held at the British Museum, include a gold ring, bars of silver, and a fifth-century crystal sphere bound with gold. “Discoveries such as this are an important part of our national heritage, and the Treasure Act is designed to ensure that such finds can be acquired by museums for the benefit of the general public,” Williams said of the collection. “When treasure is found it belongs, from the moment of finding, to the nation.”

Recovered crystal rock pendant (photograph courtesy of the British Museum/Mercia Police Department)