Thanks for the additional info. If I could edit my post I would have put Panzermantel instead of Panzerlauf.
I wonder what the post war arsenal folks did when they encountered one of these feed covers? Probably nothing if they are just checking function/fit and put them away.
I think that it would be another story for the ones that take it on the line or in combat to shoot it for the first time, and may not have closely checked.... I can't load this @#^&*( machine gun!! So the armorer just replaces the top cover and probably tosses the "bad one away" since they have plenty of guns and spare parts.
But on a serious note, I think that I will have to locally fabricate the booster retaining clip for mine, sine these are just as rare as the dismount kit.