My best guess would be that someone was working on a coin operated vending machine without the proper tools and they needed a flat head screw driver to loosen the big screw just above the coin catch box. They most likely broke the end from their pocket knife blade then had the idea of locking a quarter in the jaws of a pair of ViceGrip™ pliers and using it to loosen the screw. The jaws of the ViseGrips™ caused the triangular mark on the edge and the two lines around the edge a little farther are from the first failed attempt at locking the quarter into the pliers jaws.
I really don't know for sure that is what happened, just one possibility.
You can see how the edge of the coin is bulged out at the site of the damage. This tells us that the coin was smashed that way and it didn't happen during the striking process.