In 1940, amid adjustments to postal regulations and parcel taxation in wartime China, the Dah Tung Book Co. repurposed high-denomination definitive stamps of Dr. Sun Yat-sen into postage due issues. Originally part of the regular definitive series, the 1 and 2 dollar stamps were typographed in Hong Kong and later overprinted with large characters in black and red reading “暫作欠資” (“temporary use as postage due”). This overprint appears on all four sides, in a style commonly referred to as the No. 4 Sung character style. The stamps retained their original ornate Sun Yat-sen portrait frames—orange for the $1 and blue for the $2—while gaining new postal functions. These stamps are catalogued as Scott J67–J68 and were essential for handling high-value due payments. Both examples are mint never hinged with full original gum and even perforation. Their cultural and philatelic significance lies in the adaptation of resources during conflict and the clarity of typographic overprints reflecting practical necessity. Estimate "$120 – 160"