Mario, It is a P for Philadelphia site of one of the three mints. D for Denver no letter for San Fransisco. Some of our coins also have a VP which was the engraver I think-Fred
The f on the front of the coin is the initial of the guy that designed the
coin,not the guy that made the dies. His name was James Earle Fraser, he was a sculptor. Google his name and you can read more.
Back in the Late 1800's there was another Mint in use in Nevada at Carson City. That mint used CC as there identifier, mostly now seen on the back of old Morgan silver Dollars under the Eagle.
Arnaud, any coin can be carved, but you have to be careful on clad coins like this. The nickel layers are pretty thick, but if you carve too deep, you will hit copper. You can use this to your advantage if you carve the entire background down to copper for a cameo effect.