The amulet was dug up from remains of a late Roman cemetery in 1990
New scientific evidence has cast doubt on the authenticity of a silver amulet, believed to be one of the earliest Christian relics ever found in Britain.
The pendant was dug up from the remains of a late Roman cemetery in Shepton Mallet, Somerset, on 15 July 1990.
Markings led archaeologists to believe they had stumbled across an extremely rare Christian artefact.
Somerset County Council said further tests had suggested the silver content was as young as the 19th century.
The amulet comprises a central disc with a cross shape made from double silver beads.
The front of the 1.75in (45mm) disc is marked with ChiRho, an early Christian symbol incorporating the first two letters of Christ's name in Greek, which are similar to the letters X and P in the English alphabet.
The find put Shepton Mallet on the archaeological map and the town has named a street and a theatre after the amulet.
But experts from Liverpool University are said to be "99% certain" that the artefact is not genuine.
Stephen Minnitt, the county council's acting head of museums, said: "Following detailed analysis of the Shepton Mallet amulet, Somerset County Council can confirm that the artefact is almost certainly not the rare Christian artefact it was first believed to be.
"It is possible that we may never be able to say with certainty how it came to be buried in Shepton Mallet."
The amulet was discovered in the grave of a male aged between 30 and 50 in one of 16 burial plots in the Roman cemetery.
Two samples of metal taken from the artefact have been analysed by new technology and were found to be inconsistent with Roman silver, but consistent with silver produced in the 19th Century or later.
Councillor Justin Robinson said: "Somerset County Council is pleased that some of the mystery surrounding the Shepton Mallet amulet has been solved.
"We would be very interested to hear from anyone who can shed light on how the amulet came to be buried in Somerset."
Somerset-based archaeological consultant, Peter Leach, who directed the Fosse Way excavations in 1990, said there was "no reason to doubt the authenticity or provenance of the amulet at the time of its discovery".