That is super cool. I guess it is common to find stuff behind the walls of older homes.
When we were re-doing our basement and we tore the walls apart, written in sharpie on what looked like tinfoil (it was a cheap insulation at the time) was this: "To whomever can read this can suck my big dick." And then there was a picture of a big dick and balls with pubes and everything. Then signed by the Mr & Mrs...must have been from the 60's. Crazy to think it had been there so long, those two people probably don't even remember writing it.
lolol That is playing the looooooong game!!!
I am hoping to find a long-forgotten safe filled with gold :D