Number SCPH-30001 is the original US PS2 model. I have a original 500,000 unit and it has 30001. I'm not sure it goes beyond that. The special GT PS2 is 30050GT (I think). There are 4 or 5 versions with the newest one ending with a R. Check out some of the mod chip sites. They usually have model numbers because you need to know which one you have to buy a mod chip.
