amanico[JLC Moderator]
405521
Rolex Submariner 5514. A special Submariner.
I am not an expert on Submariners, but it seems that this one is really special.
Here you basically have a 5513, and a pretty nice one,

With a twist: The helium valve at 9 o' clock.

The screw in case back doesn't look different from a 5513.
This one is from 1977.
Some were badged Comex, others weren't.
It seems that there weren't that many made!
Enjoy.
Nicolas