I ask the question as I see many second-hand DB mount lenses (principally the Rodenstocks) being advertised at a much lower price than those in copal shutters. Even taking into account locating copal shutters and their cost it still works out cheaper than buying the lens in an original copal.

May I assume that the lower price is due to one or some (or none) of the following?

1. Lack of copal shutters now that they are no longer made (this I doubt).
2. Difficulty of converting the lens to a copal shutter due to some proprietary aspect of the Sinar DB mount specifically made by Rodenstock.
3. Difficulty of any conversion requiring specialised equipment/skill pushing the cost up to the point of not being worth it.
4. Some other aspect I've overlooked.

Many thanks,