So, I have had this stamp since I was a kid and I was always curious about the marks on it. Just above the work three there is an angled line of indentations that goes all the way to the right side of the stamp. It can be seen more clearly on the back of the stamp. There is no cancellation marks that I can see on the front. There are hinge glue marks on the back of it. Since I never purchased stamps that were expensive, I always assumed it wasn't worth much. I am just wondering what the mark on this stamp is and how much it might be worth? This is my first post. I have more stamps but they are mostly used and probably not worth much. Any information would really be appreciated.