Popularizing of Postal Code System Issued on July 1, 1968 (Showa 43) The world's postal code system has been implemented in the United Kingdom and the Soviet Union since the 1930s, but the Japanese postal code system will promote automation of the postal business by adopting automatic reading and sorting machines on July 1, 1968. Introduced for. Postal codes are assigned to post offices that carry out collection and delivery work, and large-scale offices use the station order of railway postal transportation routes and routes using the railway network, which was the center of transportation at that time. It was 3 digits, and 5 digits for other stations.Stamps were issued continuously for a certain period of time for the purpose of disseminating postal codes, and a stamp booklet was also issued at the same time.