Um, guys... this is gen.
For those looking at the caseback, the H series 183 had more spacing in the font. look here;
http://forums.timezone.com/index.php?t=tree&goto=6898946&rid=0
Looks like they added the fish and the 100 meters engravings to the caseback in a later series. On the H series, those engravings are on the case.
Also, look at the movement. The swan neck is properly shaped and the beveling on the crown and ratchet wheels is the correct depth. This beveling is something that the rep factories haven't been able to get right. Also, if you look very closely, you'll see the two almost microscopic holes that are drilled in the swan neck screw, which is by the way the correct length. Lastly, the bridge plate edges are polished to a mirror shine. Not even Marlin could make a pam movement look that good.
I vote gen.
PS: One more tell is that the jewels on the movement aren't pale pink like the reps, they are a rich ruby color.