If your talking about swirl marks in the center of the reverse . Back in the day, vending machine had change holder with screws to clamp down the change in place . Something like this one .
It very well could be what Rick suggested, or something very much like it. Back then there was also a certain type of change holder that could produce similar markings, but who knows the exact cause. More important is simply to be able to identify a way it could have been caused during the minting process, and in this case I cannot imagine even the possibility.
You're certainly welcome even if I wish I could give you an exact cause. Unfortunately, with the tens of billions of coins that have been in circulation, and the infinite possibilities as to how one can be damaged, identifying the exact cause is often an exercise in futility. You're on the right path with asking questions. Believe it or not, all this will make sense sooner than you may think.