Ken Samson, 48, discovered the stash of 16 coins in woods near the Doubletree by Hilton hotel next to the busy Swallow Roundabout on Saturday.
He said it is his first major find since he began metal detecting nine years ago.
Mr Samson said he does not know when the coins date from but it appears they were buried together and some may have Greek script stamped on them.
He said: ”There are 16 coins in total. “They are hammered coins and they look foreign possibly Greek but beyond that, at the moment, I don’t know.
“There are a few other coins coming up in the area but not in the same spot. They were definitely buried together.”
Mr Samson said he was overcome with excitement when he realised what he may have found.
He said: “I’ve been metal detecting, off and on, for about nine years but this is my first hoard.
“When I saw the first coin I thought it would just be some kind of token but when I went to pull it out I saw more.
“I began pulling them out and found about 10 in total.
“But when I got home I couldn’t settle so came back out on the Sunday and Monday to the same hole and found more.”
Mr Samson said the coins were buried about six inches in the ground.
He added: “I’m going to take them to the museum later this week to find out what they are.
“I just wanted to make sure I got them all as there are a lot of people who know the area who might have come out and found the rest.”