It looks more like they were practicing removing a mintmark. If you want to change a D to an S or a P, removing the old mintmark is the first step.
If they were trying to tamper with the mint mark only, why did they leave a bridge in the center of the MM? My reasoning is they did it on purpose. Oh well, we will most likely never know!
Yes John. He is saying they are trying to create a rarity. I am not seeing it. I think it was just a coincidence that the damage appeared in that area.