Most likely a very early version of Michael dating to his days with the brothers. Many celebrity/athletes change their autograph over time. Most are used to seeing his later autographs which look nothing like this. I guarantee they have exemplars to match this version.
MJ is all I study and this absolutely isn't legit. I've seen plenty that PSA let through accidentally. It doesn't look anything like the ones posted below this either. I've seen his signatures since he was a small child all the way thru to his death. Not real.
If that's supposed to be the autograph of THE Michael Jackson, it's not like any I've ever seen. And I've seen his signature dating back to the late 1960s.