Yes, Sharpies (markers) are on very few authentic WHO autographs,...But like Jim Morrison autographs, the styles of them do change a lot. i.e. depending on the circumstances surrounding the time, place, and "state of mind" of these individuals.
Not necessarily John,..30 years ago the Rock celebrity "forgery" game wasn't the scam it is today. Also your autograph has a lot going for it....such as older autograph book paper, the fact that Keith, many times signed in a straighter line (without the "infamous" circle around his signature, (there are Many authentic examples of straight line signatures out there. And most of all, wouldn't a forger want to use a "typical" Keith Moon as an inspiration for a forgery? the one with a circle?.....Yes probably... So the only person that really would know was Keith. So Yes, theres a really good chance that it was signed by Keith Moon. P.S. All of the others who made comments, don't really know do they. One more thing, there are many letters on the autograph that are very consistent with authentic signatures that Ive studied. And Last Many of his were signed with a Sharpie!
Well, Teresa's last reply really has thrown the cat amongst the pigeons! Very interesting points from someone who seems to be very "in the know". I would never throw an autograph away, however universal the criticism of it is. You just never know when new "proven" exemplars of a similar style will turn up.