A global search has been launched to find one of the world's most legendary instruments: Paul McCartney's original Höfner bass guitar.
The Lost Bass Project is appealing for information about what it describes as "the most important bass in history".
McCartney bought the instrument for £30 in Hamburg, Germany, in 1961, but it disappeared eight years later.
The bass features in The Beatles' music of those years, including the hits Love Me Do and She Loves You.
Nick Wass is heading Höfner's search project and has joined forces with two journalists in trying to solve the "greatest mystery in the history of rock and roll".
He has collaborated extensively with McCartney and written a book about the missing Höfner 500/1 Violin Bass.
Wass told the BBC that the famous Beatle asked him about the guitar during a recent conversation - and that is how the campaign to find it began.
It is not clear what happened to the instrument, which was put away presumably after the Beatles finished filming Get Back in 1969, he said.
"It's not clear where it was stored, who might have been there.
"For most people, they will remember it ... it's the bass that made the Beatles," Wass said.
- This story was originally published by the BBC.