Dave Crisp's find, made in April, became public Wednesday, the Bristol Evening Post reported.
Crisp, secretary of the Trowbridge Metal Detecting Club, said he quickly realized he had come across something old and unusual in a field near Frome in Somerset. He immediately decided to leave everything in place and notified the Somerset Portable Antiquities Scheme so his find could be excavated by archaeologists.
"Leaving it in the ground for the archaeologists to excavate was a very hard decision to take, but as it had been there for 1,800 years, I thought a few days more would not hurt," Crisp said. "My family thought I was mad to walk away and leave it."
The bronze coins dating from the third century were enclosed in a pot the Romans would normally have used for food storage.
Some of the coins will be on display in the British Museum from late July into August. Somerset officials hope they will find a permanent home in the county's new museum.
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