I once had a Stroud Duo-Art and am very familiar with it.  It appears
that the roll motor shown in the photo was simply replaced by a roll
motor from a different make of piano.  If you look closely at the photo
of the roll motor, you can see the empty screw holes in the deck to
which that motor is affixed, which were the mounting holes for the
original Aeolian motor.

In addition, as is shown in another photo, the original Duo-Art rotary
pump is no longer present and was apparently replaced by an electric
vacuum motor of some kind.

Barry Dennis