I am not sure there is a way to tell what set a blank back came from unless there is some other difference to the card. Personally, as in other things, I use the lowest common denominator (ACC#) for my blank backs. So if I have a blank back that came in E90-1 and E92, I will go with E90-1. It is a consistent way, if nothing else. I will have to re-examine my Miller here, which is still in my collection, for the differences to E90-1..
