I just got ahold of this. The front label says:
FIREPOWER 2000
PROPERTY OF SUNSOFT CORP.
DO NOT COPY
ROM'S HAVE BEEN ENCODED TO ITS USER
MUST BE RETURNED
Pretty cool. I opened the cart to make sure, and it sure looks like a proto to me. Two IC's are on the board, with stickers and writing in pen that says "kaybee" on both, and "IC1" and "IC2" written each. What do you guys think? I have to get some photos going soon...