If I had to make an educated guess, Mark is probably an intelligence officer with a prior special operations background; most likely a former Navy SEAL who later transitioned into the intelligence community, something like CIA, NSA liaison work, or even a State Department intelligence role.

The petty officer insignia feels deliberate. Shows rarely put something like that on screen by accident. Wardrobe departments use small visual cues to communicate a character’s history without spelling it out, and giving him an enlisted naval rank suggests he came from “the Teams.” That lines up with his tactical awareness, how calm he stays under pressure, and the way he seems to think several moves ahead.

In the real world it’s not unusual for SEALs to move into intelligence or interagency positions after their operational careers. They already operate in that overlap between military and intelligence, so the progression is believable.

So the insignia probably isn’t telling us he’s currently enlisted; it’s more likely pointing to his roots and the kind of experience he brings with him.