The photos, featuring original drummer Pete Best, were taken a year before debut single Love Me Do.
Rare photos of The Beatles performing in their early days at Liverpool’s Cavern Club have been discovered.
The images were taken in 1961, a year before their debut single Love Me Do was released.
The photos show Sir Paul McCartney and John Lennon singing, with George Harrison on guitar and a partly-obscured original drummer Pete Best.
Historian Mark Lewisohn described them as “whippet-thin under-nourished lads” following their tour to Germany.
The band, who were then aged between 18 and 20, had recently returned from performing in Hamburg, where they had been “slogging 500 stage hours in 90 days”, he said.
“So slender has this marathon made them, it’s as if their heads and bodies are stranger.
“A look emphasised by the unusual clothes – leather trousers and cotton tops. No other photos show them dressed this way.”
Mr Lewisohn, who has written a number of books about the band, said the photos showed The Beatles playing to a lunchtime or evening audience in July 1961.
“Three months from here, John and Paul went to Paris and returned with what became known as ‘The Beatle haircut’.
“Days later, Brian Epstein saw The Beatles in the Cavern, offered to become their manager and set them on a course that changed our world.”
Pete Best was dropped from the band in 1962 and replaced by Ringo Starr.