For years I, and others, have asked "What is an MS60 class passenger car?"
In general terms, it was known that the "MS" indicated a "Mail Storage" car. But since there were no cars on the roster in the 1950's classed MS, what was to be used to fill such a spot that a "Makeup of Trains" book called for?
Another known, for the 1950's anyway, was that an MS60 could be filled by a B60 (baggage) or a R50b (reefer). Without fanfare, a reefer could be hauling chilled product one day and be used for mail storage the next day. Similar situation for the B60 baggage cars.
The main quandry in the 1950's research centered on the X29 in express service. The X29 was a shorter car and the general concensus was that an MS60 requirement called for 60 feet of storage space. This would exclude the X29. So where were the X29's used? A few were called for in the "Makeup of Trains" books, but not many. And there were far more express X29's in the fleet than would be needed to meet all X29 calls in the "Makeup of Trains" books!
There was a true MS60 car in the early years. Literally dozens of these cars appear on the 1920 roster of passenger equipment. It is unknown how and when they were taken out of service, but they were definitely all gone by the time the 1954 roster of passenger equipment was published. By that time the B60's and R50b's were definitely filling that role.
In the fall of 2003, Harry Stegmaier authored a book on 1952 Pennsylvania Railroad passenger consists, through TLC Publishing. In many locations he seemed to use not only R50b and B60b, but also the X29 as a candidate for an MS60. I tracked him down and gave him a call.
According to Stegmaier, the MS60 refers to a quantity of "cubic" storage (not "linear"). He indicated that the X29 was a little higher than some other box cars of the same length and thus qualified it to be a MS60. Though the B60b, R50b, and X29 were the most commonly used cars as MS60's, he indicated that it was also a regular practice to use B70a "scenery" and B74a "horse" cars as they were seldom used in their original roles any more. He specifically excluded the use of BM class cars as they were in short supply and their priority was for working mail cars.
Ray Burghart noted that the consist book dated 10/25/1964 states on the front cover that "ALL MS-60 EXPRESS AND PAPER CARS ARE TO BE R-50 OR X-29 TYPE UNLESS OTHERWISE INDICATED." So, in later years, original Pennsy documentation clearly spells out what can fill a MS60 requirement.
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Last modified: November 23 2007.
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