OK... So this is definitely a pentastar-stamped, OEM mopar, mercury-switched lamp. Same setup as trunk. one hot lead in, grounded by connection. Comes on when it reaches X degrees angle.
Not sure where from, though. PN 4607096.
I'd say it's from the 70s, though. Or at the least, it doesn't look any more modern than that.
I'll post pics once I get it wired up. :-)