WHAT DOES BCM LOWER MEAN?

bcn complete lowerAppeared it more than so over and over and will't locate the blem. Everytime I believe I locate something off, it is just oil smudges. Best guess at this stage is scuffs on castle nut, or The 2 little silver places from the flare of the magwell. 1mm dots at most. BCM QC isn't going to mess all around It appears.Terrific lower for