Have had a Bronica S2 for a short time. Difficult to find lens info (and other info) on this old Bronica series. That's why this place is invaluable for the knowledge reservoir here. I just noticed that the helicoid of my Bronica S2 is threaded on the inside. Does this mean it can accept some screw-in type lenses? If so, does anyone know the size of that threaded opening on the S2/S2A?... IE: what "mount size" lenses to look for? If this is not the case, is there an adapter that screws in there to mount older lenses or something like that? Has to be threaded for a reason.