Some years ago I bought this at an auction sale. It was in a box with some other stuff. It is a radiator cap from a Model T Ford with a standard light bulb socket soldered to the top. Has homemade lampshade with what appears to be old time threaded christmas tree light size socket clamped to it. The christmas tree lamp holder appears to be a Bakelite compound with a metal thread socket inside the Bakelite. There are two wires (with braided insulation) coming from an oblong hole at the bottom of the Bakelite -- one just a pigtail assuming going to the center for the bulb to contact, the other I'm thinking is affixed to the threaded shell and it goes underneath the big threaded shell and is soldered to the radiator cap. The insulation is not removed where it would be a contact for a full size threaded bulb. The whole thing is painted silver.
Is this someone's joke, or does this actually have a use? (The bulb is my addition.)
Here is a "more modern" version of what you have that I picked up at at estate sale a few years ago.
This is a commercially manufactured work lamp, attaches to the radiator neck and runs off of household current (there is a plug but it can't be seen in the photos).
Electricity and water. A winning combination if ever there was one.
Oh it's just somebody's bright idea. ;o)
Charlie you are right, like chainsaws and beer. Dan
Thank you for shedding some light on the issue
Back in the day we gave those A/C lights away with a minimum purchase A/C spark plug inventory.
They worked great when the radiator cap was still in the center of the radiator. They were quite popular with the mechanics of the day as it put the light where it was needed.