Very possibly a mercury vapor[0], or low-pressure sodium lamp. Mercury vapor lamps have effectively been banned in the U. S., but that was around 2008 and your

Very possibly a mercury vapor[0], or low-pressure sodium lamp. Mercury vapor lamps have effectively been banned in the U. S., but that was around 2008 and your lamp would still be within that range. And, yeah, my experience says that mercury lights last effectively forever. I don't remember ever changing an existing bulb (not that my experience with mercury lights is all that extensive). [0] https://en.wikipedia.org/wiki/Mercury-vapor_lamp https://en.wikipedia.org/wiki/Mercury-vapor_lamp