In my research, I learned that these were possibly used in some rail cars (although I've never actually seen one in that application) ...
Ben, thanks for chiming in here.
Just to clarify the rail car confusion, yes, a nearly identical toilet (and sink) system was used extensively in rail cars, and specifically it was used in "roomette" accommodations on sleeping cars made by both the Pullman and the Budd companies. I can tell you that I have used these toilets on many occasions, and they were not comfortable or pleasant to use, but having a private facility in your own room was still better than having to use common facilities at the end of the car.
That said, I'm not certain these were the trademark "TravelLav" units. For one thing, I believe they pre-date the early 50s. For another, there is no stop valve on them. The units installed in converted coaches would have emptied into a waste tank, and so some sort of valve would be necessary to prevent tank gasses from coming back up into the bathroom. As I understand it, the stop valve is incorporated into the folding mechanism, such that when the unit is secured back in the stowed position, the valve is closed. By contrast, railroad cars of the day had no pesky waste tanks, and the contents of the toilet simply emptied onto the tracks. There was basically an open hole in the back of the toilet bowl, and when you folded the unit back into the wall, the wasted emptied out through that hole and down a short chute to the ground. No tanks meant no sewer gasses, and if you opened the unit just an inch or two you could hear the rails and even see the ground going by. Every toilet in railroad cars back then had a prominent sign warning you not to flush while the train was in a station.
It is possible that one and the same company manufactured the units for Pullman, Budd, and Converted Coach. In which case I would suspect that the lion's share of the market was the rail car industry, and Converted Coach was just along for the ride. The demise of luxury passenger rail travel in the 60s spelled the end for sleeping cars made by both industry giants, and I think the last cars were made in perhaps 61 or so. When new sleepers were built for the Superliner (and later AmFleet) trains in the 70s, laws had changed and it was no longer permitted to dump untreated waste on the trackway. Toilets installed in these later cars could not use gravity alone, and most are either vacuum systems like those on ships and planes, or macerating systems. The waste goes to a central tank. A system such as the TravelLav simply can not be used in such an arrangement, and I suspect that was the end of that product. With Pullman and Budd out of the picture, it would make sense that CC purchased what was left of the production.