|Proofs reveal the process of postage stamp
production and add dimensions to the stamp collection or exhibit.
The purpose of the die proof was to check the progress of die during various
stages of production. These proofs were taken usually
or after the die had been hardened and were
thus marked "BEFORE HARDENING" or "AFTER HARDENING". Die proofs
were also taken for the purpose striking molds to test for damage and are
marked "BEFORE STRIKING" or "AFTER HARDENING." Some die proofs
were taken after plate numbers or check letters were inserted, but the
plate numbers were not always the actual numbers to be used for the printing
of the finished plate and the check letters sometimes used for the die
proof were not the same size as the final check letters used for printing.