This was on a dusty shelf in a dark corner of Universal's lamp dock.
I had no idea what the hell this thing was (I stood and looked at it for a while, with my head cocked to the side like that dog in the old RCA ads) - I ended up having to hunt down one of the older guys to tell me.
It's a DC (Direct Current) underwater light from the 1950's. There's not a good sense of scale in the photo, but it's about two feet (60 cm) tall.
Back in the days before specialized underwater lighting systems, electricians would take a bare 10k (10,000 watt) globe, epoxy (the gooey looking grey stuff) the connection to make it waterproof, drop the bulb in the water and turn it on. This was how they lit the pools on all those old Ethel Merman movies.
This one is clearly an attempt to build a better mousetrap, and has a metal reflector to magnify the light, a steel cage to prevent bulb breakage, and a weighted plate on the bottom to keep the whole contraption near the bottom of the pool (light bulbs - even big ones - float).
Wacky. I can't believe the lamp dock still has these things. I'm almost positive they're not allowed to use them anymore.