Marker Across the top of my books
Hello, This is my first post and I have a question for someone with more experience than I. I recently attended a comic convention and while there I picked up a copy of ASM 300, New Mutants 87, Hulk 340, Secret Wars 8 and Wolverine 1988 issue 1. All appeared to be NM copies however I removed one of the books from it's bag and noticed that the top of the book had been marked with magic marker specifically green magic marker. I continued to open the other books and every book but the Wolverine copy had the same marker across the top. The marker doesn't bleed into the covers nor does it bleed into and of the inside comic panels. The marks are the width of the comic and about 1/2 inch in length. I will mention that the ASM 300 is a newsstand edition but none of the other books are so I don't believe that to be a factor.
Does anyone have any insight as to what this does to the value of the books? Are they still worth grading? Sorry I have no pictures but I'll try to add some tomorrow. Any insight is much appreciated!