Zamo, "forced matched" is where someone, such as at an aresenal (that is what everyone wants to beleive
) or more likely private USA individuals "make" a part the same numbers or style of the other parts. In other words, forced the parts to now match the gun.
I have no idea what a GNR is... It has something to do with Porteguese lugers, but I have never understood where the GNR abbreviation comes into play...