dummy stamp

It is more accurately described as a printer's sample stamp, or dummy stamp.

A dummy stamp is a stamp-like label which is not valid for postal use.

Test stamps are a form of cinderella stamp and in the United States are also commonly referred to as dummy stamps.

The stamps are not intended for use and are therefore to be distinguished from test stamps, though both test stamps and printer's sample stamps are dummy stamps in the broadest sense of that term.

Dummy stamps are a form of cinderella stamp and the two principal types are test or training stamps, used to test postal equipment or train postal workers, and printer's sample stamps created to promote or demonstrate the printing capabilities of a stamp printer.

The term has been in use in the U.K. since at least 1949 when reports of proceedings of the Royal Philatelic Society, London referred to a display of "dummy stamps" produced in connection with the negotiation of a printing contract for the postage stamps of South Africa.