Counterstamps outside of the mint. No real value beyond 1 cent, but a lot of people like to find them. People just passing the time, you can have a stamp made for ID and stamp coins, although some find damaging coins distasteful.
These are fun coins to save. If look close you will see that there is two different imprints of Kennedy. There are many different design.
I like this one. Seen a lot of counter stamps in my day. But not this one. I believe the pipe is quite fitting.