About Printer's Proofs: Before a poster was printed in large quantities, the printer would print a limited number of test posters. Commonly, they would leave the color chart on the edge of the poster, which added an extra inch to the width of the poster (which explains why the poster measures 28" x 41"). These would then be shown to people in a position to "OK" them. Once they were approved, the final posters would be printed and the proofs normally were destroyed.
A printer's proof is far more rare than a regular one sheet poster, and there is no fear of purchasing a reproduction. It was issued for international use only Send me your question about any possible Romanian poster and I will answer you immediately.