Mail train question

Does anybody know what railroads cars where usuall on pennsy mail trains?

Atlantic Coast Line, New Haven, Pennsylvania, Missouri Pacific, just to name a few. Baggage cars were used for storage mail, and did tend to wander off-line. Basically, any railroad that interchanged with the Pennsy might end up having head-end cars running on the Pennsy, even on mail trains.

If you do a Google search of "PRR train consists" you might find a document or two which includes mail trains such as this document from 1960: http://www.multimodalways.org/docs/rail ... 4-1960.pdf

Mail storage cars could be baggage cars or passenger-equipped boxcars (such as PRR's X-29 boxcars). Such cars also doubled as Railway Express Agency cars (which also had its own cars), so were used for baggage, storage mail, and REA service. On a PRR train, most would be PRR cars (they had a humongous number of B-60 and R-50 cars), but there would be others in the mix, too. For example, New Haven baggage cars in REA or storage mail service were not total strangers to Los Angeles Union Station via the AT&SF (Boston to New York via NYNH&H, New York to Pittsburgh and St. Louis via the PRR, St. Louis to Kansas City via MP or CRI&P, Kansas City to Los Angeles via AT&SF).