The Spilsby Hoard, which contained 281 coins, was finally knocked down for £600, well over its high estimate of £350.
It was bought by The London Mint Office, a company that supplies coins to collectors across the world and specialises in historic and modern commemorative coins.
“This hoard tells a fantastic story, from its burial right the way through to the find,” said a spokesman for the London Mint Office.
Made up mainly of bronze coins featuring the emperor Constantine the Great and members of his family, the hoard is thought to have been buried around 340AD. They were discovered in 2014 by two Midlands metal detectorists.
“It is not that unusual to find the odd Roman coin but to find an entire hoard is very rare,” said one (the pair wishes to remain anonymous). The detectorists added that it was the biggest collection they had ever found. The proceeds from the sale will be split between the finders and the landowner.
The majority of the coins were produced in the Roman mints at Arles, Lyon and Trier, with additional examples struck in Siscia, Aquileia and Rome.