Does anyone knows the correct filter size for a Leica 35mm Elmarit-R lens V2. According to the Leica Wiki it's a Series 7, based on the serial number (#2787xxx see below) and the two metal prongs on the outer lens rim. But the Series 7 filter retaining ring doesn't fit (second picture). It's slightly too big. A series 6 retaining ring also doesn't fit (first pic). It's too small.
The outer circumference of the lens seems to be about exactly the same as a Series 7 filter. So, it can't "drop in." And Series 6 are way too small.
What am I missing? Are filter's held by a hood? I think that's the case with the series 6 version of 50mm Summicron. But it still accepts a retaining ring, I think. ... If so what size are the filters?