Interesting question, Mark, and as always, interesting feedback from Chris.
While I have absolutely no information regarding C-class engines, I know you know that all the C&S narrow gauge engines had triple valves on the tenders.
Somewhere I had gotten the idea that the FRA had required triple valves, cistern water level check pipes, and emergency air dump valves on all tenders. #74 was fitted with the air dump pipe and valve on the RGS around 1950.