What I have learned is that they made them until 1969, these are the older ones, depending the color, red for sure has uranimun. Then in 1982 they started making them again. I have found out that most of hers are earlier then 1982, but she contiuned to collect it, so she has a mix match set, of various color. So now I have to find out more, thanks for the info, I'm going to start looking for pieces now too, amazing what is collected, I just thought they were plain ole' plates. P.S. don't eat off the early red ones.