Good eye, I remembered what to look for on the safety. I just about fell out when I saw it.
The follower has an early slide but look at the hole, it is "D" shaped, not round. I found two of these. Not real sure how to identify a rev. 1 from a rev. 2 . The numbers stamped on this one is somewhat of a mystery.
The middle trigger guard is the first rev. 1 without an SA, that I have seen.
I saw some other unique parts . One of the more interesting ones was a windage knob with crosshatch checkering.