Today I removed the grips from my S&W 686 6 “, to check and tighten the strain screw as I was getting light strikes. The photos show a series of letters struck on the metal of the gun. There seem to be a lot of them but I don’t remember any marks on the 686 4”, which I part-traded for this revolver. It’s a Target Champion model which I believe were sent to Germany. Anyone have any idea as to their meaning?