Thanks...
Mine will make a slight movement when I put my finger against the ring or shake the camera. The ring does not appear to move back and forth, but I can hear some type of movement in there. Yours is perfectly solid against the top plate?
I would agree with your thought that it is there to keep out dust. In any case, it does not seem necessary, as my other camera bodies (of different make but similar vintage), have no such part and they do not seem to have a problem with dust or debris. I like being able to pick up a camera, and get that "solid" feel--no shakes, rattles, or movement whatsoever. I have put aside my OM-2N because the Winder II does not mate well to be body. With some pressure, I can move it back and forth...not a solid feel.