280's Second Line

Jason:
I don't belive the second line is for air, it was used to supply steam for the San Juan's consist.
I have a picture somewhere which positively shows coach 280, distinguishable by her three sets of lamp vents, in the San Juan. As the car is in the consist, not at the end, there would have had to be a means to pass steam to the other cars from the locomotive. By the way, 280 is painted "Rio Grande Gold", with silver trucks and double stripes.
Other coaches which may also have been used in similar fashion in those years (meaning used with passenger equipment fitted with steam heat), probably included #306 and #284, which were both fit with bay windows for use on the Chili Line, and #320. All of these cars were later used on the "Silverton", although 280's career was cut short moving to Boulder in 1951. The other three were used at least until 1965, because they all show up in service in the Don Winslow collection at urbaneagle.com.
I am quite sure this is the answer to your question.
Mike