Sketches including designs for Sir Paul McCartney's "magic piano" that were found in a skip could fetch £10,000 at auction.
Builder Andy Clynes, 54, found them in 1999 as he converted a mill into a wine bar near Manchester.
He put the sketches in his loft but recently decided to get them valued. They will be auctioned on 24 March.
Sir Paul played the psychedelic piano in The Beatles' 1967 Magical Mystery Tour film.
The sketches were among other papers found by Mr Clynes including a handwritten list of commissions for 1960s art collective BEV.
Mr Clynes, from Oldham, said: "I picked them out of the skip.
"The case burst open as it was thrown in. It was raining and I just picked up what I could.
"I imagine there was a lot more there but it was damaged."
The sketches and designs for Sir Paul's piano will go under the hammer at Omega Auctions in Newton-le-Willows, Merseyside.
Auctioneer Paul Fairweather described the papers as a "rare find".
Mr Clynes added: "I've had them for 20-odd years. You put things away and forget about them and then something triggers your mind.
"I haven't planned what I'll do with the money yet but I was surprised about the value."