In my catalogues I overlooked one rail: Horseman on their recent cameras not only offered telescopic rails, but also a simple twin-dovetailed one (regular only on their LB-camera). Looks to me as a close match.
It is still available, now offered more pronounced.
Ok everyone. Thanks a million for the help. I did scrounge up a used Horseman rail from fleaBay cheap enough, and it is the correct rail.
This is one piece out of the way. I've identified my rail.
I still have a few questions, so if someone has a fair degree of Horseman expenrience can you contact me please?