Yet another "X-ray" novelty--this time, 1901's X-Ray Cathodoscope
From Boyce's Monthly, June, 1901. I'm betting this is yet another take on the X-ray Wonder Tube. "Tells time on watch through cloth"? Possible meaning: The X-Ray Cathodoscope can see through cloth, at least when the cloth is covering the face of a watch. That's my guess. Actually, "tells time on watch through cloth" sounds like something out of a magic act.
Yes, the highly cheap paper is as yellow(ed) as it appears in the scans.