Colchester Museums have re-dated a gem to Rome's Republic.

The engraved gem, a deep red colour, was mounted in an iron ring. It would have been used to seal letters and documents.

Experts have revealed the ring to date 150 to 250 years earlier than previously thought.

The intaglio was excavated at Gosbecks Archaeological Park, Colchester in 1995 by the Colchester Archaeological Trust. It was unearthed within the area of a ‘Romano-Celtic’ temple.

The new information came to light when Colchester + Ipswich Museums Service launched their Collections Online database.

Revd Dr Martin Henig, an expert on ancient engraved gems, identified the armed figure as the god Mars, but the shape and style of the ring and its gem date it to the second century BC and no later than the first century BC, long before Emperor Claudius’ invasion of Britain in AD 43.

Glynn Davis, senior curator for Colchester + Ipswich Museums Service, said: “This is a fascinating object that potentially suggests a long, personal history, changing many hands over centuries, before it reached the capital of Roman Britain.

"Mars was, perhaps not unsurprisingly, a popular deity amongst the Roman military and this ring might have arrived in Britain on the finger of a legionary, having been handed down generations of their family.

“The revised date of the ring provides the attractive alternative that it was owned by an influential Iron Age Briton, perhaps a hi-ranking chieftain.

"The name of pre-Roman Colchester – Camulodunum, meaning ‘Fortress of the War God’ – gives an insight into how popular and important the god was to the Iron Age Britons of Essex.

"The native god of War – Mars Camulos – would have been worshipped here long before the Roman conquest and perhaps the figure on this ring was perceived as such.

"In either case, of the thousands of Roman rings discovered from Britain, this is one of relatively few dating back to the time of Rome’s Republic.”

Councillor Julie Young, the council's portfolio holder for Culture and Performance, said: “Having such a precious item in the Museum's collection is simply incredible."