[SENTINEL]

It is not the weapon, but the cradle. The cradle looks to be some specialized unit for naval use, it's not standard.

If you look closely, you will see that the weapon itself if very nicely oiled.

I'm afraid to say, this is a navy problem, not the young marine standing there!

[Ronin]

It's a squid, not a Jarhead, manning the gun. Still, lousy shape for the mount to be in and the ammo looks damn scary.

No GMC worth his salt would ever let a mount deteriorate into that state.

[El Gato]

I'm afraid to say, this is a navy problem, not the young marine standing there!

That's a sailor, not a Marine. Draftsman 2nd Class Arturo Chavez according to the caption. If he was a Marine, LadyX would personally be out there chewing on him, and Texas Cowboy would be haunting his a$$.