From your description it sounds like it could of been a bastardized SG-X.
I believe they were made in the mid 80's.
You can check out EverythingSG.com for help identifying it. They're SG nerds!
EDIT: Here's a nice specimen on eBay.
Well, even though it weighs a ton, it's not the kind of guitar you play for a three hour set, y'know?
I'd still love to get one, but I don't think I could cough up the dough for a Gibson unfortunately.