Sometimes I put 4 black stripes down the edges of the stack of halves, but I always put 3 or 4 black stripes on the wrapper, no matter what coins they are. I've done pennies, quarters, and halves, plus 3 rolls of dimes.
If you are buying your coins by the box, they will have been rewrapped by the coin counter. I do mark my roll wrappers but they will only show up if someone bought my rolls and then cashed them into another bank in the same rolls. I never buy from the banks that I sell to.
I think this is a good topic. It is interesting to see how far coins can travel. In another post, I told of a half with a Jacksonville Fl. phone number ingraved on it that I found here in Calif.
If I find any marked halves other than the ones that the vending machine people have marked, I think I'll start mentioning them on this forum. See if it was from anyone here.