The thumb eater was a B3-2, the same as mine. He had probably shot 6-800 rounds through it when it failed. It had worn enough, "not hardened", to the point where the latch failed and the lever closed. I never had that problem with mine, and am guessing by the dust collection on it, never will!
I am looking for classic German or at least a classic rifle that is collectible. Be Well,Gator