Issued on August 9, 1945, during Japanese occupation in central China, this mint never hinged set comprises four airmail stamps denominated from 150 to 1,000 Chinese dollars, each bearing a red "S" overprint symbolizing air-raid protection funding. Printed by gravure in yellow green on unwatermarked paper, these stamps were adapted from the earlier Great Wall airmail issue and show a dynamic aircraft flying over rugged terrain with the iconic Great Wall in the background—representing national defense, aviation, and landscape motifs. The overprint marked the stamps for use in restricted postal zones under military administration during the final phase of World War II. Catalogued as Scott IM 9N111–9N114, Michel JP-CC 104–107, Yvert JP-CC PA8–11, Stanley Gibbons JP-CC 128–131, and China Stamp Society CN-IM SN148–151. All examples are fresh and well-preserved, with full original gum and vivid impressions, suitable for advanced collections of occupation and wartime postal history. Estimate "$260 – 320"