I have no expertise at all in autographs, but my gut tells me this ball is real...I do think it's hard to believe that a forger would get the exact 1927 ball for the 1927 team with what little knowledge was/is out there regarding balls...the crowded sigs and perhaps deliberate could be a sign that the guys wanted to make their best signature for Combs, and perhaps he even told them to make sure where to sign and to not make it too big since he had plans to get everyone on it.
Just my completely uneducated opinion.