The crank codes are based on the Japanese Imperial calendar. Whenever a new emperor took the throne, a new era was officially declared. On December 25, 1926 Emperor Hirohito ascended to the throne and chose the the name Showa (radiant peace) for his era. It ended on January 07 1989 when Akihito took the throne and the Heisei (peaceful accomplishment) era began. Thus, 1926 is year 01 of the Showa era, 1927 is year 02, up to 1989, which was Showa year 64 and Heisei year 01. This Japanese Imperial Calendar was used by a number of Japanese bicycle and component manufacturers but dropped as they started to expand into international markets.