I am in the process of rebuilding the Angelus diaphragm pouch action
out of my Bradbury Artrio Angelus piano.  Something that has me a bit
bewildered is that on the output holes of the primary valves (that is,
the holes in the valve board that are tubed to the larger secondary
valve pouches) there is a strip of paper glued across the length of
the edge of the board so as to cover the air holes.

Very small holes are punched in the paper effectively restricting the
air flow virtually back down to the size of the tracker bar holes.
This is original from the factory as I have another Angelus action from
a different piano that has the same thing.

This doesn't make sense to me as I would expect you would want the full
size hole to exhaust the larger pouch?  Seems like you are defeating
the purpose of having the initial primary valve.  Has anyone else
encountered this?  Can anyone explain the purpose of it?  Obviously the
factory put that there for a reason.  Thanks!

Dave Krall