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: Imperf or perf is 11 1/2 on white paper. Forgery: Imperf, perf 10 1/2 or 11 1/2 on browning, faded paper. There is some loss of detail.