Yeah I've always felt that the 'J' wasn't right. I've looked up a few Jagger autographs and never saw a loop 'J' like that. Still I thought I'd ask to see what everybody else felt just incase :)
This one is not authentic. I have one where he only have signed Mick J. But that J is different from this. I almost should say fake to mine if I didn't get it in person.