Someone emailed me about how to identify seen from rear busts. I tried to make my answer as simple as I could, hoping that I did not oversimplify it. Of course, not all busts are exactly the same and the three things I pointed out might not always be so evident or even present (specifically the line on the neck). Below is my message along with an A2 bust type that I highlighted. I have also included an A4 bust, which is draped and cuirassed.
Seen from the rear busts are actually fairly easy to tell apart when you know what to look for. Take a look at the A2 bust, to the left of the bust (below the right shoulder of Constantine II, where his arm might be) there is a sharp line that slightly angles up. On a regular bust, that area is usually more rounded. The rear type usually has a somewhat triangular shape on the chest from the cloak, slightly showing a bit of the cuirass. Sometimes there is a small line representing the neck muscle. I have attached the A2 picture from my page with yellow highlighting of the three things I just wrote about.
