http://www.lighting-gallery.net/gallery/displayimage.php?album=230&pos=0&pid=118169It looks like a 1960s/1970s version of today's P17M by General Electric? Other than that, I don't know much more. I am surprised to see that there are still some out there. I used to be in possession of one and the date on it said 63. I am assuming it was a date code because it was a 100W HPS, so it was either a conversion, or it was made sometime in the 70s with some weird date code. Any ideas.