Issued on June 20, 1940 and printed by Commercial Press Ltd. in Hong Kong, this used complete set of 20 airmail stamps ranges from 15 Chinese cents to 5 dollars. Each stamp features gravure-printed depictions of aircraft soaring over sections of the Great Wall and dramatic mountain landscapes, symbolizing national pride and China's aviation aspirations during a time of war and reconstruction. Perforation is variable, and the paper bears the small multiple “YU” watermark (upright). Catalogued as Scott C21–C40, Michel CN-IM 359–378, Yvert et Tellier CN PA21(A)–PA30(B), Stanley Gibbons CN-IM 545–564, and China Stamp Society CN-IM AM29–AM48, this set is a visually striking example of wartime airmail issues. All stamps are used with clear postmarks from various locations including Nanking, Hankow, and Shanghai, with generally fine to very fine centering. Estimate "$280 – 340"