The art of Forgery
Most of us always think of Forgery as an art of imitation of an rare document/artifact with an inexpensive substitute. However today some stamps of the master Forger Jean De Sperati are more valuable than the stamps he imitated. Some like this one are valued about 100,000 USD per postage stamp.
The only 2 distinguishing feature from the original are:
1) the discolored faint break in the horizontal lines. (inside the box)
2) Signature of the the Forger on the stamp.