The history of M. Welte & Sons, Inc. is thoroughly explained in the
book "Welte-Mignon, It's Music and Musicians", by Charles Davis Smith 
& Richard James Howe.  It is currently out of print but copies can be
obtained.

As a point of interest, the 1929 Boston organ could not have been
built by M. Welte & Sons, Inc. per se, because they no longer existed
as a corporate entity.  Throughout most of the 1920's the successors
to M. Welte & Sons, Inc., traded as Welte-Mignon Corporation.  However,
because of several reorganizations, the firm was likely trading under
another name.  Refer to the Smith-Howe book for more information.

Mark Reinhart
Charles Town, West Virginia