Nothing suspicious about it. I get them stamped from time to time. I suspect it is to verify the count (50 rolls) and height tolerance of a roll (over/short rolls). Of course, I suppose they could poach enders, but I suspect that some of these individuals aren't too bright. For awhile I was getting boxes that were inspected in the future.
I'm sure it's just to verify that the box had enough rolls and maybe to identify who it was inspected by at the company. I thought those boxes came from Coin Wrap Inc.