How about the early Welte-Mignon "Red" system?  This has a double-valve
stack that is all glued together.  The pouches are all zephyr skin.
I don't have a good source for zephyr skin.

I would never take on an H. C. Bay player with all its pot metal
(including screws) and Bakelite valves.  I am working on a Wurlitzer
Recordo grand right now with pot metal valve casings.  These have
warped considerably, causing leakage.  A previous rebuilder used a
rough nap leather for the valves.

I also ran into having to figure out a schematic for this as there are
none available.  What the last "player person" did, tubing-wise, did
not look right to me.  The valves were made of cardboard spacers with
a Bakelite stem.  This cardboard had warped badly.

John Tuttle sells the Wurlitzer unit valves (I wish I knew that before
I spent most of a day rebuilding five unit valves).  The pouches were
bad and the hardest part of the job was I had to make these wooden
rings that held the pouches in.  I replaced the cardboard valves with
wooden upside-down Ampico valves.

I am just getting paid to get the player working again and not to
rebuild it.  A piano moving company goofed by forgetting to put the
screws in one of the legs; that's who is paying me.  The pianos owner
swears it "worked" before it took "The Big Fall."

My other job right now, is a single valve Standard player action in
pristine original condition.  Any experienced player system rebuilder
with an aptitude for it can almost literally do these in their sleep.
On the Wurlitzer job, I have people doubting my competency right now.
Whereas, on the Standard job I am _certain_ that I will be "the hero."

The owner of the piano is going to turn 93 years old.  She has fond
memories of this player piano as a little girl and her family and
friends bonding over it.  It stopped working in the 1960s.  I am
invited to her 93rd birthday party.  We are going to surprise her as
she has no idea the piano is being restored.  Her family bought several
rolls including "Happy Birthday."

Here is a discussion thread I would like to start:  "These Player
Pianos All Have a Story," just like the movie, "The Red Violin."

Bill Maguire