This closet appears to hold the tools used in setting pop valves and performing hydrotests on the various locomotives. The tubes bent into a circle are gauge siphons. They protect the gauge when connected to steam by condensing water in the lower part of the loop and keeping live steam away from the gauge. The tools in the bottom of the picture with the "T" handles on them are pop valve gags. They are used to hold a safety valve closed during hydrotests and may also be used to keep the lower pressure valves from opening while the high pressure valves are set.