Also known as the "Eye lid" or "Silent" Studio shutter.
I have two of these which came built into Studio cameras.
All the Studio cameras I have seen in Denmark and Sweden have either the Grundner or the lokal NORKA (like a double door Guerry - but designed to fit behind the lens board).
One is not working, although the bellows eye-lids are undamaged.
I have no idea of what is inside the activating metal cylinder but it is held together by just two screws. I don't have access to X-ray equipment.
I will be working on this the coming week. If anyone has either a cross section drawing - or better still, real live experience - please post.
In lieu of this, I'll post my discoveries, good or bad as work progresses (or is abandoned)!