Yes, at ChipGuide I show an Assoc. Bonne-Nouvelle plaque where the protective layer was pulled back by the casino as a cancellation. It provided the collector to still have what looked like a plaque in its original state of preservation on one side. What I did with my examples from the club was to clean them up my removing the messy pigment and having what seen in the photo. There are also delaminated plaques known that were previously drilled that hade incused serial numbers, but when either side was defaced the holes were filled in and a new protective laver placed over the plaque not showing any holes drilled... and no serial number. Just explaining that it is not just chips that can be altered.