By Paul Burnell
The One Show
He once sang Give Peace A Chance but it seems the teenage John Lennon might have been less of a pacifist.
The record card was nearly destroyed
The man, who returned his MBE because of Britain's links to the Biafran War, was possibly an air cadet.
A card showing Lennon's apparent Air Training Corps membership was found when The One Show staged a Beatles memorabilia roadshow in Liverpool.
Beatles experts say the card - which has yet to be authenticated by the ATC - may cast new light on Lennon's youth.
The card clearly shows "Lennon, John Winston: Next of Kin: Mrs M E Smith (Aunt), 251 Menlove Avenue, Woolton and Employer or School: Quarry Bank High School, Harthill Road."
It now belongs to firefighter Tom Mills following a fire at the city's Speke Airport in the 1970s.
Beatles fans say the possible ATC membership casts new light on Lennon
The card lay in a box containing ATC membership records which Tom was told to throw out as firefighters cleared up after the fire.
The three experts on hand to spot fake Beatles items were very excited at this potential insight into the star's early life.
"I had no idea that Lennon was ever a member of the corps," said Stephen Maycock, rock and roll memorabilia expert who has worked with Bonham's and Sotheby's.
"So this is adding a piece of the jigsaw which as far as I'm aware no-one's every heard before."
He added: "This fact is a new fact to me, it's a fantastic thing."
Tom Mills (right) found the card working as a firefighter
The item is believed to be worth at least £1,000 to £1,500 according to antiques dealer Curtis Dowling, who said: "Collectors are now struggling to find pieces that are unique rather than just important."
Stephen Bailey, owner of The Beatles Shop in Liverpool who authenticates a lot of Beatles memorabilia, agreed: "As purely an important piece of local Liverpool history yes it's got to be worth at least £1,000.
He added: "Strictly as a museum piece its priceless."
The ATC's historian is checking the authenticity of the card.
You can learn more about this story on The One Show, BBC One 1900 GMT, Monday 18 February 2008.