This has been on eBay for quite awhile. It's being offered by Strawberry Walrus, I believe. Some time ago, I read on his website that supposedly the fan who got it signed asked Paul to make it special, so Paul took it back from the fan and signed "James" in front of his regular signature, James being his legal first name.
That's the story, if I remember correctly. But, of course, the real question...is it real?
But there is a Ringo starr signed letter ,that ringo wrote to an astronaut because every morning they used to wake up to Ringo's song.
Great one for Zarelli.