A rare John Lennon and George Harrison-owned fretless guitar just surfaced - and it's worth over $500,000

Antiques Roadshow has seen its share of strange objects over the decades, but guitar geeks will surely be taken aback by one of the latest artifacts to be exhibited on the long-running series.

A prototype fretless electric guitar, manufactured by Bartell's of California in the 60s and once owned by both John Lennon and George Harrison, made an appearance on Sunday's episode of the show.

Currently owned by a guitarist, identified as Ray, who once played on sessions for a film company co-founded by Harrison, the guitar has been valued at over $500,000.

Ray says he first got a hold of the guitar when Harrison himself suggested he use it during the recording session.

"I played a few notes and he said: 'Yeah, you're definitely getting more out of it than I am,'" Ray told the BBC. "'It's doing better for you, why don't you have it'." Befitting its unique looks, he also described the instrument as a "a strange old thing to play."

The oddball looks and playability of this guitar certainly haven't impacted its value, though. Antiques Roadshow expert Jon Baddeley said "I think in 25 years it's by far the most expensive thing I've ever seen."

For his part, Ray said "I never really thought about value, as George being a mate and all that.

"I didn't realize it was worth that much money. It's lucky I don't keep it in the house."