In the course of restoring a Wurlitzer IX-B, a piano with mandolin
and 14 bells, the need was to fill the changer full of APP rolls that
actively used the multiplex system of simultaneous "on/off" pedaling
perfs to operate them.

I found that Wurlitzer didn't even begin cutting those controls into
APP rolls and using the charming 14-note bell section until after 1920.
I sought rolls with serial numbers indicating issue from 1921 and
later, resulting in at least two tunes on the 5-tune roll having bell
sections and appropriate control holes cut.

Actually, QRS masters were used from the early 'twenties on.  The best
Wurlitzer APP arranging (in my opinion) was done prior to WW1, and
bells were not a feature on the earlier APP machines.

Stephen K Goodman - Professional Player Piano & Nickelodeon Restoration
Tarpey Village (Fresno/Clovis) California, USA
http://www.mechanicalmusicrestoration.com/ 

 [ Dave Bowers, in the book "Put Another Nickel In", says that a few
 [ Wurlitzer LX instruments were fitted with a xylophone as well as the
 [ 14-note bells, and the APP rolls had multiplexed controls for both
 [ the bells and xylophone.  What notes does the xylophone play?  Where
 [ are these instruments today?  -- Robbie