The images were captured in July 1961, over a year before the band released their debut single Love Me Do.
They show John Lennon and Sir Paul McCartney at the microphone, with George Harrison on guitar and a partially obscured Pete Best, the group’s original drummer.
Beatles historian and author Mark Lewisohn said: “Set inside Liverpool’s cramped and dank Cavern Club, these previously unseen photos capture The Beatles playing for a lunchtime or evening audience in July 1961.
“Just back from Hamburg – slogging 500 stage hours in 90 days – The Beatles are whippet-thin under-nourished lads of 20 (John), 19 (Paul and Pete), and 18 (George).
“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.
“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.”
To mark the 60th anniversary of Love Me Do’s release, Chorley-based dealer Tracks Ltd is offering free rare music memorabilia valuations.
The valuation day takes place at The Beatles Story exhibition at Liverpool’s Royal Albert Dock from 11am-6pm on October 5.