Things are valuable in proportion to their scarcity. The rarest and most valuable Chinese stamp is not the earliest "customs dragon stamp," but the stamp which carries the nicknames "king of Chinese stamps" and "the world's one and only" --the "red stamp marked one yuan."
物以稀為貴，目前我國最罕貴的郵票，並非是最早的「海關大龍票」，而是有「國郵之王」之稱的「紅印花加蓋小字『當壹圓』」。