I have aRodenstock 135mm Rodagon which Bob Salomon tells me is about 25 years old. I asked if there have been significant changes in these lenses since that time and his answer was that they are constantly evolving, that the glass from mine will not fit in the current model (I hadn't thought of trying that particular trick!). I do know Nikon greatly improved their El Nikkor (it became N) around 1980 They changed both the mount and the glass, and ar least the 50mm went from mediocre to excellent.
What I am leading up to is, when purchasing used, does anyone have any ideas as to the vintage of various enlarging lenses vis a vis their quality. I know to avoid the old Nikkors, even though they may be 'mint'. But what about Rodenstock and Schneider. I also have noticed Schneider changed their mount a while back, but what about the glass?
Camera lenses seem an altogether different proposition. There is a lot of information out there. But does anyone have any ideas regarding enlarging lenses?