Pneumatic Card in Balloon: vintage

I believe this to be German made.  It has a pneumatic release.  The items is functioning in that you can release it as a normal card in balloon but I can’t get the pneumatic part (which delays the release) to function properly.  There is a spare gasket if you can figure out how to install it. There is also a screw on the end which i think sets the pressure.  There is also a cover plate which goes over the loaded card which i have never seen on any other model (see photo).  I believe this to be a fairly rare piece.

The height is 15 inches and the base is 3 by 5 inches.