Having done a ton of research on this card we honestly believe it is unique to date. We have found blank back test issues and even some hand cut test issues with a back, but in addition to being hand cut they are also WAY out of register. We cannot locate a single other example of a 1968 Superman Test which appears to be machine cut with a back. The techincal grade of SGC 1 is due to damage to the edge of the card, what appears to be press grab marks, but other than that damage it is a sharp card with great color and registration. Logically you can't print one card so there may well be more somewhere, but we can find no evidence of another one ever coming to market.