You’d think that the world would’ve run out of priceless Beatles memorabilia to auction off, but every once in a while, a previously undiscovered artifact seems to fall out of the sky. That’s the case with the lost acoustic guitar that John Lennon used when the Beatles were making Help! — both the 1965 album and the movie that shares its title. Lennon’s guitar is the most prized item in a new music memorabilia auction from Julien’s Auctions; it’s up for sale today in London.

As the Julien’s Auction’s website reports, John Lennon used his Framus 12-string acoustic Hootenanny guitar in recordings and performances of songs like “Help!,” “It’s Only Love,” and “I’ve Just Seen A Face,” and George Harrison played it on “Norwegian Wood.” In the scene from the movie Help! where the Beatles sit around their living room and play “You’ve Got To hide Your Love Away,” that’s the guitar that Lennon plays. The guitar, long thought to have been lost, was recently rediscovered in an attic, where it had apparently sat undisturbed for 50 years. Its estimated worth is between $600,000 and $800,000, and it’s expected to fetch more than that at auction.

As Beatles artifacts go, this is right up there with Paul McCartney’s previously lost Höfner bass, which was just returned after 54 years. At a previous auction, another one of John Lennon’s acoustic guitars sold for $2.1 million. The latest Julien’s auction also includes instruments and clothes previously owned by people like Michael Jackson, Freddie Mercury, Joan Jett, Tina Turner, Amy Winehouse, Adam Clayton, and Mick Mars; you can find more details here.

UPDATE: It sold for $2.9 million, setting a new record for a Beatles instrument sold at auction.