Sources say it is...
A very reliable source said it's Mike during his psycho phase when he would run naked in the streets.
"1"
Who is your source?
First time I looked at it, I would say it's NOT him. I don't think it is, unless the juice messed with him THAT much. But I don't see that happening back in his day.
The haircut is different, as is the mustache, and obviously the size of him. But I'm going to say that it's not him...even if it's posted in Arnold's own gallery.