Republic of China Airmail Stamp, 15 Sen (Yuan) with Plane over Great Wall

This item is an airmail postage stamp from the Republic of China, featuring a biplane flying over a mountainous landscape with a section of the Great Wall of China. The primary color of the stamp is a deep teal or greenish-blue, printed on what appears to be off-white paper. The stamp has perforations along all four edges, indicating it was intended to be torn from a sheet. In the lower left corner, the denomination '15' is prominently displayed in a bold, sans-serif font. The lower right portion features Chinese characters, which, based on the context of 'airmail stamp' and 'Chinese stamp', likely denote the denomination in Chinese currency and 'airmail' or 'air service'. Other smaller Chinese characters are visible across the lower center of the stamp. The scene depicts a single-engine biplane flying horizontally across the top middle, above rolling hills and a distinct stretch of the Great Wall with a watchtower on a formidable peak to the right. The artwork is rendered in a somewhat illustrative style, typical for stamps of this era, suggesting a period before highly intricate photographic reproductions became common. The condition appears to be used, as evidenced by what looks like a cancellation mark or postmark obscuring some of the central details of the landscape and text. This mark consists of an array of small, dark, irregular, and slightly raised shapes, possibly indicating a date or location, though it is not clearly decipherable from this image. The perforations are mostly intact, with no obvious major tears or missing sections. This type of stamp would likely date from the mid-20th century, possibly from the 1920s to the 1940s, a period when airmail services were gaining prominence in China.