Interesting. It would make sense that they would make new ones for each film considering how many hours they get worn. I had never noticed the differences. What that link doesn’t mention is that the OT mask was asymmetrical. They scanned half of it, mirrored it, and printed an exact mirror copy to create the ROTS mask. And it is supposed to be new and pristine. I had always assumed that no all Vader’s opponents had gone down without a fight and in the finale of Rebels (and I’m assuming anyone who wants to watch it has seen it already) Ahsoka got in a good blow that damaged the right side of the mask. I’m assuming that is to partly explain the asymmetrical nature of the mask.