I purchased 3x500rd cases of 180gr 40S&W from LAX ammunition at a really good price. For some reason they felt the need to remove all the 50rd boxes from the original cases and ship the ammunition to me in three different boxes. In the process they managed to ship me three different lots of ammunition. One of the lots has headstamps with a PPR marking. I've never seen this before. Any idea what PPR stands for?