Any info on these 50bmg muzzle brakes

[6cmShooter]

I have these 3 50bmg muzzle brakes that I know almost nothing about other than that a friend of mine who use to work at Mcmillan said they were off there tac 50 rifles. When he gave them to me.

 

[secondofangle2]

I know that the one on the right appears to be fractured so I wouldn’t use that one lol

 

[stefan73]

I know that the one on the right appears to be fractured so I wouldn’t use that one lol

Looks like casting marks?

 

[secondofangle2]

Because it's a clamp-on style, I'd make damn sure before I used it. I'm talking about the area around the clamping neck, looks suspicious to me.