A unique Beatles demo of It's For You (1964), a song the band wrote for fellow Liverpudlian Cilla Black, realised £18,000 ($23,542) in an August 28 sale.
It was the star lot of Liverpool Beatle Auctions' sale in the city's famous Cavern Club.
John Lennon introduced Cilla Black to manager Brian Epstein in 1963
Black, who died last year, was a cloakroom girl at the venue while the Beatles were beginning to take off.
She became a close friend of the band.
They were instrumental in helping launch her career as a singer - in fact it was John Lennon who introduced her to manager Brian Epstein in 1963.
Black's version of It's For You charted at number seven in the UK charts.
This acetate is the only known recording of the Beatles playing the song.
It was found in a pile of records that Black's family brought to the Liverpool Beatles Shop to have appraised.
Stephen Bailey, the store's manager, explained to the Telegraph newspaper: "We got to the last one, and as soon as I heard it, I thought, 'Oh God, that's not Cilla Black. It's Paul McCartney.'
"I was shaking with excitement and speechless. I realized that this was the long lost Beatles demo disc from 1964, and I was probably one of the few people to have seen and heard it in over 50 years.
"Apart from a few crackles, which you get with acetates, the quality is fine. It's a wonderful recording."
Please sign up to our free newsletter to receive exciting news about music memorabilia auctions.