If you compare it with a normal black 5 cm f 2, you can see that instead of that chrome filter ring, there is a fitting black ring, but only the same hight as the other rings.
The inside ring (closest to the lens glass) has not the same shape as on a normal black, it is slightly different
It seems that some lenses lilke this were produced, but does any one knows more about this ? number made ? why was it made ? etc
thanks




