This unusual plug interfaces an electric hair dryer to the 120V 60Hz mains. The thing that makes it peculiar is that when it is tipped back and forth, a small 'clunk' can be felt, as something inside shifts in response to being tilted.
It is a small boxy thing, about a 1.75" x 1.25" x 1", has no ground lug, but is polarized. The wire coming out of it almost certainly carries 120VAC. There is a molded-in warning not to replace, open or immerse the plug. There are no openings of any kind, nor any obvious ways to disassemble it non-destructively.
What would clunk back and forth inside there? It probably isn't an isolation transformer, not in a box that size, for 1800W. I doubt it's a tilt sensor, but can't rule that out. A replacement fuse might be about the right mass, but wouldn't be much use in an box that can't be opened. Anyone know what this is, before Mr. Plug is introduced to Mr. Hacksaw?
Mr. Plug's mugshot ..
No buttons of any kind. That metallic looking spot where a screw might ordinarily be is absolutely flat, and doesn't move. There are two not-screws like that, the other one is not visible in the picture, being hidden behind the right-hand prong.
follow up ..
After removal of the cover, a circuit was revealed:
Turns out that the the thing that went clunk was that inductor in the foreground. Interestingly the connection on the right side failed, so the loose inductor was just wagging up and down. You can just see the hole in the wiring board where the lead was meant to connect.
Best Answer
I was inclined to say it was a ground fault current interrupter. However, those that I am familiar with have manual test and reset buttons.
I did a search to see if an auto-reset version exists, and apparently it does.