Help ID ar15 barrel

[legion3]

This is a 14.5 inch m4 cut barrel with a YHM-28-5C2 Phantom 5C2 Comp/Flash Hider.
It is marked

MP 5.56 Nato
1/7 CB

I understand the codes on the barrel except MB?

It sits in a LMT upper with a Predator custom shop, Knoxville TN lower.

My question is is this an LMT barrel? Are they so marked?
If not any idea's what barrel make...

And I am not a member at AR15.com so please don't redirect me there.

Thanks