Autopianos were built over a period of roughly twenty years.  Different
models were made concurrently and, during this long course of production,
many changes in construction occurred, mainly to simplify the mechanism
and/or to reduce production costs.  Generally speaking, the later
instruments do not allow enough space for the installation of an
earlier player action, or extensive alterations will be required in
one, the other, or both.

Here is a representative sampling of Autopianos I've observed over the
years:

Auto Pneumatic Action:
  Studio model, 65-note only
  Studio model, 65-88 note
  Conservatory model (taller than Studio), 88-note only

Auto DeLuxe Action:
  (Medium-sized instrument, very well made)

Standard Player Action, single-valve:
  (Autopiano by this time essentially identical to Kohler & Campbell,
Francis Bacon and other makes built in the same factory.  Casting
bearing name bolted to pin block but separate from plate.)

In addition, the Auto Pneumatic Action, one of the finest player
actions ever built, was advertised as "Used in 90 per cent of the
Highest Grade Player Pianos".  In larger instruments, the Auto
Pneumatic Action is found to have stack pneumatics significantly
longer than in the smaller.  Renamed during the early teens "Auto
DeLuxe" or "Standard" (depending upon grade), it became one of the
most popular makes.

Jeffrey R. Wood