Tom,
  I'm not sure I understand.  Was this car being used to transport cylinders ... or whatever
was -in- the cylinders?  

  I suspect this car was not in service for very many years - that it would have been
replaced by a tank car quite soon after it went in to service ... sort of a "proof of
concept" approach to transporting propane/what ever by rail.

  Does any one have a date for when tank cars first started being used for propane/etc.?
                                                                                                                  - Jim B.