The short-cross penny, which is still in very good condition having been preserved in the soil for centuries, dates from the 1260s.
A SILVER coin dating from the 13th century reign of King Henry III is among the medieval finds uncovered by archaeologists in the Walkergate area of Berwick.
"This date and the quality of the building's construction suggest that it may relate to the medieval heyday of Berwick," explained Chris Burgess, Northumberland county archaeologist.
"It appears to have been slightly disturbed by some of the later pits and robbing, but should be in a comparatively good state of preservation, having been largely protected by the depth of the dark-earths that overly it.
"We won't know more until we can expose more of this by removing them."
Archaeologists from Tyne and Wear Museums have been working on the former Beehive site for over two months prior to construction work starting on the new £3.3 million business start-up units.
Early in the dig they found the foundation walls of three separate buildings, the one nearest the road thought to date back to the Elizabethan period.
These three phases of building seem to show how the street has become wider over the years, with a progression from early to late from the front of the site to the back through a series of different buildings gradually moving away from Walkergate.
However, the team were always confident the site would throw up some older archaeology given Berwick's rich history and that has turned out to be the case.
"As expected, several walls and a possible floor are now visible in the sill-beam trenches," revealed Mr Burgess.
"At this stage, it's hard to see exactly what this means. What seems most likely is that we have a building with good quality stone walls and floor extending east to west in the southern part of the site."
The team were also recently given the go-ahead to extend the excavation site slightly to the south to match the final building footprint more closely.
Mr Burgess said: "We have hired in a JCB to take off the majority of the garden soil and are quickly recording any features that we encounter in this area.
"This means that we can make a start on digging the various sill beams and the lift-shaft that go much deeper than the majority of the excavation area.
"This is our best chance of investigating the earlier medieval deposits from a time when Berwick was, in theory at least, much more densely populated than it was in the later periods that we have been looking at so far.