Luke Myers talks about his Steger Natural Player Action system.
I have seen more pictures of this stack than those posted and, yes,
it took me a few minutes to figure out what the heck they were doing
when it was designed.  It is unlike any other I have worked on for
the last 40 years of doing so.  The valves are upside down in a way
similar to Amphion valve blocks.  However, I see no reason that this
stack should not work perfectly well with a good quality restoration.

The hole in the pneumatic back is in the thicker than normal top
board of the pneumatic.  There is one hole that supplies the pneumatic,
and there is another hole that serves as the outside seat of the valve.
It has a channel straight out the back side of the board.

It makes valve travel a bit more difficult to set but the vent hole in
the back is there only to allow air back into the pneumatic when the
valve has deactivated from the tracker bar.  If these holes are plugged
the notes will try to stay on all the time and may activate without any
signal from the tracker bar.

I can certainly see why a novice rebuilder would think it makes no
sense to have that hole until you sit down and think about the system
in its entirety.  Then it does make perfect pneumatic sense.

The problem here is Luke is on a very short budget and on very short
time and wants a functional player piano ASAP.  Impatience is the
biggest problem to player restoration I have ever seen.  Luckily it
is easily solved with practice being patient.  This is probably not
the ideal player for Luke him to start his rebuilding with, but I have
coached him in a few things so that perhaps he can take my emails and
get it going.

Of course the best course of action would be for him to take a few
days and bring the thing to our shop where he can rebuild it under
supervision, which I did offer him but it is a good 6-hour drive and
he is in college so time is limited.  It would take him two to three
days to learn how and to rebuild his valves and perhaps another day
or two to take care of whatever _else_ is wrong with the system, as
someone has rebuilt it in the past and we know better than to trust
previous repair work very much!

So, Luke, it is not hopeless even though it may look like it right now.
The system is sound and once all the valves are refaced and regulated
and all the leaks hunted down and destroyed that player system will
play as well as the day it was sold on the showroom floor.

Doug L Bullock
http://thepianoworld.com/ 
https://www.facebook.com/doug.l.bullock