This is in reply to Craig Roothoff's questions regarding Duo-Art
long play top actions.  There is an article about this in the AMICA
Bulletin of December 2008 (vol. 45 No, 6).  It has many pictures.

In brief, the Duo-Art long play top action first appeared in pianos
in 1928.  This dating is based on serial numbers in the pianos.
Initially there were some questions about this method of dating,
from the standpoint that the pianos themselves might have been
"unsolds" that were used for experimental purposes.  However I'm told
that Steinway did not give Aeolian serial numbers for the pianos
Aeolian bought from them until the player action had actually been
installed.

The long play Duo-Art top actions predate the marketing of long play
drawer model Ampicos by two years.  Examples of this configuration
built as late as late as 1935 have been reported on.  One of mine has
a roll drive motor with a 1935 serial number on it.  This spool box
will easily take the Ampico "B" spools.

The two Duo-Art top actions I have include the kind of roll tightening
brake which one sees on a B Ampico.  Close-up pictures are in the AMICA
Bulletin previously referred to.  The one pictured has different sized
needle and bleed from the one in the Ampico B.

Unlike the Ampico, we have a lot more vacuum available to work with.
Because of that, the brake can run evenly for a longer time and has
a wider range of strength than the B Ampico.  I have a number of rolls
which, using the kind of paper the Powells used, fill a Jumbo B spool
to the brim, and they never slip at all.

It's a great idea, those vacuum play brakes.  Someone should make them
available. They should be designed with the fact in mind that they must
function well with a wind motor.  Wind motors do not have the strength
the electric motors have.  There must be a way that would be easily
attached on most pianos with the least possible alteration of any
original construction.

Bruce Grimes