On 05/13/2022 12:20 AM Jim Mischke <jmischke@...> wrote:

Yes, the M-15k wagtontops were used as cores for M-15n and M-15p wagtontop rebuilds.   The M-15k population was consumed quickly in the purest biblical sense.   For B&O modelers, this 1955-56 M-15k - to - M-15n/p is a notable and precipitous transition for rolling stock selection.

A main difference between the 1955-56 rebuilt M-15n and M-15p subclasses is that the M-15n's were 40-ton capacity, the M-15p's had 50-ton capacity.    The difference was not in the car structure but in the plain journal bearing capacities in the trucks used.

Ever the wear-it-out-patch-it-up-make-it-do B&O was given to reapplying brake gear and trucks to rebuild programs and cars built new from builder kits.   Much depended on what other cars were being retired at the time.   Paperwork was kept matching up donating car carcasses and their recipients by road number, for a safety audit trail.

Attached are two photos from the Tom Underwood collection at the Barriger library illustrating M-15n and M-15p.   Rather large raw files, I hope they come through.