Because of - we'll be nice and call it "an omission" - of all the facts of the case as presented on the FOX broadcast, Bob Shell (the man who verified the footage) has since been extra-careful to explain he was only given three frames of film. (A similar three frames were sent to Kodak.)
Mr. Shell recently uploaded a .gif of those three frames to the CompuServe Mufon Library in the Encounters Forum... and here is one of them. They're part of a continuous sequence and virtually identical, so we've only included one for faster viewing.
(If you can spare the bandwidth, here's the entire 260 kb .gif.)
Wow, actual 1947 film... of a doorway. But what doorway? There's no doorway visible in the autopsy film at all - this could be an image of the door to the men's room at Shea Stadium for all we know.
So what does this prove about the age of the autopsy film? You decide.
Several months and endless requests later, Mr. Shell still has not received any original film showing the alien itself, nor has Kodak or any other testing agency. (Start holding your breath.... now!)