New manuscript, very old news. At the time the movie was released in 1970, Butch's sister, Lula Parker Betenson, was still alive and even then insisted that her brother survived well into the 1920s and possibly 1930s.
Many books have been published on the subject, and whether this manuscript turns out to be authentic, wrong, or a hoax will not make a bit of difference. Well, if it can be proven authentic it might mean something, but what are the odds of that?
Here is the best book I've read on the subject.
http://www.abebooks.com/servlet/Sear...assidy&x=0&y=0