One of these stamps is a genuine stamp and the other(s) is a forgery. Can you tell the difference? If you are having trouble, see the "hints" and answer below.
Genuine: The genuine have round “O”s and the “S”s with the base appearing to point level or downward, in the words “FRANCO BOLLO” and “POSTALE”. The forgeries have oval “O”s that lean to the left and the tail of the “S” points slightly upward.