I have an Ali signature on a Neimann poster promoting the Ali-Frazier fight, actually it has Frazier too, and it looks a lot different than this.  I've always thought the poster signatures to be real.  Getting them verified might be a problem, I think everyone wants posters dismounted, and this one is glued to its backing.

First two scans are the.....really odd sized paper, maybe 8 x 16", I couldn't get it on one scan, the last one of the poster.  The background on the poster is really white, at night my camera makes white go brown.

Thank you again.