I bought a IIIf body and, separately, a collapsible Elmar 3.5/50 lens (pre-1946). Both appear in excellent condition. The lens is a bit stiff in pulling out and locking. When I focus, though, the lens tends to turn with the focusing ring. When I hold the lens and try to turn the focusing ring separately, it blocks. I have no (recent) experience with collapsible Elmars, so I wondered if this is as it should be or not.......