Mad Squirrel

I"ve had my Gibson SG custom showcase edition with 2 EMG pick-ups since 1990, I played it for several years, so obviously there is some wear on the neck and a few dings on the body. I haven't played it in several years and I've been trying to find out what it is actually worth. I'ts the same colour as the SG in this thread. Serial # 80698570. I would appreciate any information or direction to go to find as much info as possible.