Thanks guys!
I guess I knew it would be almost impossible to ID for sure with no maker's mark. Maybe I will just have to settle for it being so unusual. Jeff and Will, I have included a closeup of the "tag".
It was attached with screws for sure. It could have been to mark for loss prevention, or maybe to cover the mark on the pattern, when the maker was merged.... It sure looks like the mark to really identify it would have been under this tag. If that was their intent, they certainly succeeded. I'll have to keep an eye out on Ebay to see if anything like this shows up, but then the seller wouldn't know what it was anyway.
Oh and Will, my father's one and only skillet is a GSW. I did not know this until about 6 months ago when he finally allowed me to clean and season it for him. Many years of buildup!
Chris ;)