These photos show John McClelland's nice Mason & Hamlin piano with a Welte-Mignon player system installed at the M. Welte & Sons factory in Poughkeepsie, New York.  The piano serial number is  "Op W966", and the Mason & Hamlin records indicate that serial number 966 was built in 1913.

The Mason & Hamlin factory supplied the piano to Welte in a special case, so that extra depth (about 20 cm, or 8 inches) was available for the player system components.  The case measures :

  height: 147 cm (57.88 inches)
  width: 167 cm (65.75 inches)
  depth  : 81 cm (31.9 inches)

Yes, it's a big piano!  Sometimes a door frame must be disassembled so that the piano can move through.  And of course it weighs much more than the weight of an ordinary vertical piano.  The piano movers groan.

John says that the player system was installed in Poughkeepsie, New York.  It is a "transistional" system, meaning that some of the components were built in Poughkeepsie while other components came to New York from the Welte factory in Freiburg, Baden, Germany.

At the top right corner of the cast iron plate can be seen" "Mason & Hamlin   Boston, U.S.A."  This is the only place where "Mason & Hamlin" is shown.

In the photo below, at the right of the spool frame, a modern electric motor has been installed where a pneumatic airmotor normally would be.  That's the only change in John's piano; everything else is restored like it was in 1913.