I'm going to revive this to see if anyone can at least tell me what that ring is called: it is a very thin ring that sits behind the filter ring and in front of the aperture ring. the only thing on it is the white dot for setting aperture. Thus it is supposed to be stationery. Mine now turns freely. I will not be using nail varnish on this lens.
Can anyone help with terminology so I can at least search for a solution?