I came across some older 870 Wingmasters (70's & 80's vintage) from a police department that are marked in block lettering in the upper left hand side of the receivers with "PIMC COMBAT". The stamping looks like factory markings, not aftermarket. About 8 of the 40 shotguns I saw were marked this way. I haven't been able to find any info on the web. Can anyone help with info? Thanks in advance.