For it to be a legitimate mint error, there would have to be evidence that it could have actually happened in the minting process. Since the blanks (planchets) are stamped out, and then go to a machine (upsetting mill) that rolls the rim, it would have to be in the rimming of the coin that it occures. Once a rim is applied, it would go to the dies which would stamp the obverse and reverse designs along with the reeding that is in the collet. If it isn't capable of being done there, I doubt that it was a mint error. Hopefully someone with error coin experience can tell us some more. This is just my guess on how I would think it would happen.