Playing a Notse Intelligence Game in Spain

A wild body appears in the atlantic ocean. The player needs to discover this body, absolutely believe it's authentic and pass it up the chain. Our dead body is going to have disinformation in two places on his body and in a brief case. It's going to be a letter between generals ny and alexander of allied command s. But since this is a top secret mission, anyone who finds this will likely believe this for the rest of their lives.