RF bezel on IVsb2?

[rbiemer]

A while back I got a decent IVsb2 and noticed it didn't have the bezel/ring around the RF window. So I inquired here at RFF about it and got good info:
A) it is decorative--I mean hat it's not holding the glass in place--and I can still use the camera with out it.
and
B) these rings are often long gone by now
and
C) the ring from a FED2 camera will fit.
So, I got a ring from a FED2 and it looks OK to me(though likely NOT to a Canon purist); much better than with out it.
My questions about this :
Was there an equivalent of the Leica OKARO (or ORAKO?); the filter to increase contrast between the RF/VF? Or does the Leica accessory fit?
Or some other accessory that would screw into place there?
Not a world shaking worry or anything but it's been in the back of my mind when I use the camera. And I thought some of the truly knowlegable folks around here would know or have some better informed speculation than I.
Thanks!
Rob

[VictorM.]

I don't think Canon made anything like an OKARO/ORAKO (I always get the two types mixed up). The diameter of the rangefinder bezels on my Leica IIIf is 11mm. Before you buy the overpriced contrast filter, snip a small piece of colour film, with the orange base, and put it in front of the rangefinder window. It may not add much to focusing ease.