I picked up two slabs from ebay because they were very reasonably priced. They are in good shape, but there are markings that border the book itself in the plastic enclosure. I am pretty new to collecting cgc certified books but I do have a few purchased from reputable comic stores and none of those have any of these sort of markings. Are these signs of a case that has been tampered with, or are these commonly seen in some slabs that have been through a process that I'm not familiar with? I hope the images show the markings off clearly. I sure hope they have not been tampered with as that would really suck. I should add that both of the books added to my registry set successfully with the cert. numbers on the label. They are not really expensive books or anything so I don't really suspect counterfeit books, but it just looks like the cases have been opened to me. Again, I'm not sure what the deal is here so hopefully someone can shed some light. Thanks.