Panerai is Panerai since the invention its box 1950 with its "crown guard" system before the SLC, the 3646 or as want to call, were not more than a instrument watch, with a common design at the time and a borrowed machine that really is what to you become...
and a bit..personalized. I suggest buying a couple of books about Panerai and pouring throught them. For example, you've forgotten the "transition" cases (not a..box...) 6152/6154. The fact that the original Panerais were TOTALLY assembled with ROLEX comp...