I have buckets of coins that look vandalized, but they are detector finds and many were damaged either unintentionally or by nature. Coins take on different colors depending upon where they were found, and the type of soil and water. Other forces also act on them, such as being caught between rocks and bent as the rocks are moved in the surf. Silver coins from Minnesota fresh water lakes often come out with a nice blue patina but very little other surface damage. Silver coins coming from salt water are usually black. Other coins come out green or brown. Coins found in mowed lawns are often hit and damaged by mowers. Those found on beaches sometimes get damaged by beach cleaning machines.
Here are a few detector finds that are damaged or discolored.

The one obvious vandalized one in this photo is the clipped penny. It shows the marks of shearing. The nickel is questionable. Maybe the victim of lawnmower. The dime is saltwater discolored. I think some of the other bent ones were damaged between rocks in the surf. I've found lots of bent coins in the surf.
Of course there are superstitions that involve bending coins too, so it is hard to say.
I know the photo is poor, but thought it would serve present purposes. I can take good photos of individual coins if desired.
Also metal detecting people often end up disocloring coins while using various methods of cleaning to put the coins back into reasonably spendable condition.
Edited by TBR
12/29/2018 10:57 am