Very unusual, a first for me. Put me in the mind of possibly being part of some sort of a set . Did a search on Goggle on the name, but did not come up with anything conclusive.
Hey you wont believe this but i just saw one of those yesterday.It's a nautical lens(Spell?). somehow a sting of lights goes in there .a scallop fisherman from portland showed me. hope that helps hoss
Yeap, Brian got it right. Scandinavian boat light for small fishing boats. Three little bulbs, red for port and green for starboard, and hang it from the boat as a marker. Sort of water proofs the lights. There are larger early ones for candles.