This striking 6-sen blue stamp was issued by Manchukuo, the Japanese-controlled puppet state established in Northeast China. The design presents a masked laborer wielding a sledgehammer beneath a formation of Japanese military aircraft, symbolizing wartime industrial strength and aerial might. The imperial chrysanthemum emblem crowns the composition, reinforcing authority and loyalty to Japan. Issued during the early 1940s, these propaganda-themed definitives reflect the intense militarization and state messaging of the era. A highly collectible item for those studying WWII postal history, occupation issues, and Asian political philately.