The player mechanism is a Hupfeld-built one.  Hupfeld built instruments
with 73-note scale and 65/73-note players turn up from time to time.
I should guess this was converted to 88-note operation later in it's
life.  I guess the instrument was originally built some time between
1905 and 1910.

Adam Ramet

 [ Colin Campbell confirms your guess: "I meticulously counted the
 [ tubing from the stack to the tracker bar (in situ).  There are
 [ 73 tubes from the top of the stack to the tracker bar."  -- Robbie