MYSTERY: The dog tag. FULL LIFE: Cyril McCarthy and his wife Frances on their wedding day in 1919.

AN extensive search for the owner of a lost World War I dog tag has finally come to an end.

After an investigation stemming from northern France and travelling through the Hunter on its way to Sydney, the relic will soon be returned to Private Cyril Michael McCarthy’s relatives.

Private McCarthy could be considered one of the lucky ones who fought in the Great War.

After three years of service he managed to return home to marry his childhood sweetheart and lived until he was in his late 80s.

Although he has since died, his dog tag will at least return home to his grandson more than 95 years after it was lost.

French history buff Valentin Henon discovered the identity tag while metal-detecting around a paddock close to his Campagne-les-Boulonnais home in northern France.

He made contact with Lost Medals Australia founder Lieutenant Colonel Glyn Llanwarne OAM in an effort to find any living relatives earlier this year.

Lieutenant Colonel Llanwarne, who has ‘‘re-homed’’ more than 1300 medals, managed to track down the soldier’s grandson, Bernie McCarthy.

‘‘It came out of the blue,’’ Mr McCarthy said.

‘‘I suspected he was doing a bloody survey or selling something, I was very sceptical.

‘‘But now I’m very happy that the dog tag will be returned.’’

Private McCarthy was born in Newcastle in 1891, signing up for service on December 22, 1915, and serving in the 33rd Infantry Battalion.

He fought at the battles of Messines and Passchendaele in Belgium and was twice wounded in action before being sent home on September 15, 1918.

He married Frances Daniel in East Maitland in 1919 and brought up three sons – John, Leo and Daniel.

Lieutenant Colonel Llanwarne said he was proud to once again return a war relic to its rightful home.

‘‘This is purely a hobby, just an interest of mine,’’ he said.

‘‘I guess I’m devoted to the service and my grandfather and father had their own medals so I do what I can do to preserve other soldiers’ memories.’’

Mr McCarthy, who lives at Collaroy Point, said he had no idea his grandfather’s dog tag was missing, but has a number of his war medals safe at home.

‘‘[Cyril] never spoke about the war with me,’’ Mr McCarthy said.

‘‘He had a reputation as a hard-nosed, tough and bombastic sort of man but he was a decent bloke, known as a character and a larrikin.’’

How Private McCarthy happened to lose his dog tag will forever remain a mystery.