It might be their initial
If you are reffering to a simple "P" on the arm, I'm pretty sure it's a pirate thing. I didn't research this, but convicted pirates reportedly were branded or tattooed with a "P" to show other people what they did.
It means that 2 pints equal a quart. This is called a Ditloid, where you replace a key word with its initial letter in capitals. 2 = P in a Q means 2 = Pints in a Quart.
There is no 'P' in "facebook."
2 = Pints in a Quart
2 = Pints in a Quart
88 keys on a piano.
No. some of his original paintings were never underlined. It was later that he underlined his name. I have an original Picasso that was not underlined. but he did always capitalize his P. If you can find early Picasso's that were not underlined they can easily be worth many millions. Good luck and best wishes.
In a letter, "P. S." means "Post Script."
pastrami
props
permit