Dr. Sun Yat-Sen stamps of 40,000 denomination of the Third Shanghai Dah Tung Print were overprinted in black as air mail postage stamps. In a vertical line on the right side and a horizontal line at the bottom in the shape of a carpenter's square is the overprint〝國內航空郵資已付〞(domestic air mail postage paid) in No. 5 Sung characters. The character〝湘〞(Hsiang, abbreviated name of Hunan province) was separately overprinted in the upper top corner.