Hello MMD.  I was pretty sure our local piano rebuilder had a player
with a Hupfeld action in his workshop but it took me a week to get in
there for a look.  The piano is a Richard Lipp & Sons upright.  The
Hupfeld player action is an 88-note one, with an air motor that looks
just like the ones in Welte players that I have seen.  I have sent
Robbie a photo of the motor end of the upper action.

A good deal of the expression controls is visible above the motor;
I didn't have time to sort out what did what.  Not surprisingly the
tracker bar looked just like an Aeolian 88n bar with Themodist slots.
At the bass end of the piano case, rather out of focus in the picture,
is a metal Hupfeld plate.  The writing on it says Hupfeld, Piano Nr.
40105, Apparat Nr. 36868.  The upper action has a lot of plated metal
parts in it.

I have a 73-note (Hupfeld) Claviola pushup myself.  It's roll motor
looks like an Aeolian motor lying on its back, with three double
pneumatics and a celluloid dust cover over the sliding valves.  The
motor and all the gearing is of a very high quality.  The pushup is
full of metal tubing and is very heavy.  The bottom-to-top rolls are
very hard to find; I have only about 50 of them.

Regards from John Phillips in Hobart, Tasmania.