Re: xKCC Parlor Car

It's basicaly a water tube boiler. The expansion tank is at the highest point of the system (the telltale "bump" in the roof". The drawings/ads I've seen for them have a strange "safety valve" using a rubber ball in it. It looks like it would act to release any excess pressure, and also open in a vacuum. There is fairly large diameter piping that winds along the sides of the passenger compartment and underneath the fixed seats.
When railroads were trying to develop a better system of heating, there was a conversion kit offered to heat the baker system using steam from the engine, and still be able to fire the baker heater when steam was available. This was replaced by the "vapor" system that used an adjustable low pressure regulator on each car to control the heat from the steam trainline.
It would appear to me that the majority of the heating system is intact on this car.