Your right, i think they were called super notes or something similar to it. Iran was another country that made great counterfeit US currency. When the Shah was in power we gave him the identical presses and paper that we used to produce our currency at the time. After the Shah was thrown out they started up the counterfeiting to support their revolution or so the story goes. All they needed were the plates, they already had the correct printing press and paper to produce US currency. I think there's a good chance Iran sold North Korea the presses and technology that the Korean's used to make those Super Notes which were almost perfect copies of our $100 bill. Even banks had trouble identifying the bogus bills. They were that good.