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Urkunden Prüfgebiet: USA (Unions-Ausgaben ab 1847)
Prüfer Art des Attestes Katalog KatalogNr. Crowe, William T. (Sonstiges) Attest Scott 526 PSE, Professional Stamp Experts (Prüferkommission) Attest Scott 551 The Philatelic Foundation, (Prüferkommission) Attest Scott 56 Crowe, William T. (Sonstiges) Attest Scott 581 PSE, Professional Stamp Experts (Prüferkommission) Sonstiges Scott 594 Crowe, William T. (Sonstiges) Attest Scott 651 PSE, Professional Stamp Experts (Prüferkommission) Attest Scott 689 The One Cent Franklin Plating Archive, Richard Doporto (Sonstiges) Attest Scott 7