Was wondering about the "penciled" number series on various parts of my rifle. Although serial number (M512897) is definitely stamped, not electro stenciled, on all parts except piston, most parts show 26298 stenciled on them. Bolt carrier has the 512887 stamped onto it. Piston has what looks like "7K" stenciled on it.
Stock has the M serial number deeply stamped into it. Can't see any sign of scrubbing but the stock looks new.
Finally removed the stock and saw barrel has the 26298 stamped on it. So, were these parts replaced at factory refurb?