An amplifier used by George Harrison on the Beatle's iconic Sgt. Pepper's Lonely Hearts Club Band is up for sale after its history was uncovered by accident.
Its prestigious past was discovered after it was borrowed by former New Order bassist Peter Hook for a recording session and broke down.
An engineer, who was brought in to fix it, opened it up and found Harrison's name scratched inside.
Researchers then tracked down the amp's history and found a photograph showing it being used by Harrison.
The Vox UL730 amplifier, which was also used on the 1966 album Revolver, will be sold on Thursday December 15 at Bonhams in Knightsbridge, London, and is expected to fetch between £50,000 and £70,000.
Stephen Maycock, Bonhams entertainment memorabilia consultant, said: "Very few amps used by the Beatles have come to auction before, and to find one that was used on two such significant albums is truly rare and exciting. Beatles fans all over the world will be eager to own such an important piece of music history."
Other fab four memorabilia on sale include an autographed copy of their Please Please Me album, estimated to sell for around £10,000, and a collection of photographs of John Lennon taken during a visit to a radio station in 1975.