Many of the figurines were cheaply made, and looked it. The collectibility of OJ is that it covered a specific 6-7 year period in our history. There are many fakes out their now, especially those that portray black persons, so you need to be careful. If you have a suspicious piece, try nail polish remover. If the markings come off - it was a fake.
Bisque pieces are most highly prized and much harder to identify for authenticity.
The bisque will absorb the print and is near impossible to remove. It will ruin the piece. I hope I've helped you a little and didn't give you more than you wanted. You can go to e-Bay or Yahoo and run a search on Occupied Japan and see many items up for sale, to give you some idea of where the pricing is going. Most of the serious collectors I know are disgusted with the outrageous prices being asked for the lower valued items out there.