Hello,
I have come a couple of times across a reference to Dagor lenses where it was mentioned that some of them can be changed or that a back-piece can be removed to change the characteristics of the lenses.
I have a couple of Goerz Dagor lenses
91/2in. f6.8 Gold Dot
6in. f6.8
Both lenses are in mint condition.
I am not sure if anything can be changed on these lenses but I am curious what this is all about.
Dagors are convertible. If you remove the front cell, the rear cell is around 80% longer than the focal length of the combined cells (I'm sure someone will come in with the exact conversion factor here). It won't be as sharp as the complete lens, but it will have a lot of coverage, and won't be too bad stopped down.