The correct term is “muzzle brake”. It brakes or retards recoil by redirecting muzzle gases.
For Al’s rifle, from Wikipedia, “...the U.S. military declared the A2 flash suppressor as a compensator or a muzzle brake; but it is more commonly known as the “GI” or “A2” flash suppressor.”
The M16A1 manual doesn’t say “brake” or “break” that I recall. Also the Marine Corps manual calls them a “compensator”.
I’ve found instances for both but the key is “suppression and compensation” in the FMs.
Regardless, my point besides getting dogged off about what the correct term is, my main point was that you couldn’t tell anything about the “brake/break” because it had the barrel cover over it. You couldn’t tell whether it was a birdcage or what it should have been for that time, probably a three-pronger.