Japan-China Fiber-Optic Cable System - International Society of Postmasters, Series 1976, Silver proof medallion, Franklin Mint. An agreement between the Shanghai Post and Telegraph Bureau and KDD, Japan, to lay a cable between the two countries was signed on May 29 1974. The 850 km cable was manufactured by the Ocean Telegraph Company, Yokohama and laid in 1975 by KDD Maru. The cable opened for service in 1976.