[Leon]

Hi Anson
Sorry I can't help with your particular question but it doesn't surprise me at all that you have found some on different stock. These shown are from my previous collection. The W572 in the group, which is red, is different than any other I have seen (there are probably others). I think there could be a lot of reasons but running out of paper stock and using another probably makes some sense. Maybe there was a delay in the original stock delivery and they had to substitute the other for a while? The W513s were regular ones. Fun stuff....