1966's Series Stamps Luminescent Print Issue Issued on 1966 (Showa 41) In 1966, the Ministry of Posts and Telecommunications developed a prototype for automatic sorting and stamping of mail, and issued a "luminescent stamp and postcard" (phosphorescent detection method) on a trial basis at the Omiya Post Office in Saitama Prefecture. However, since the number of printing processes is high, the cost is high, and the maintenance of the machine is time-consuming, the efficiency of the "automatic stamping machine" developed after that by color identification was superior to that of luminescent stamps. Development was discontinued and only the above two stamps were released to the public.