These coins were discovered during the recovery of the Tang Shipwreck, a 9th century vessel that was en route from China back to the Middle East when it sank off the coast of Belitung Island in the Java Sea. The coins were discovered fused together, indicating they had originally been strung together on a length of rope or a rod of wood or metal that passed through the square central hole. The majority of coins have an inscription that reads Kaiyuan tongbao [開元通寶] (containing treasure of the new beginning). This refers to a new coinage system introduced by the first Tang emperor in 621 AD and in continuous use for almost three centuries. After 845 AD, a mark identifying the relevant mint was introduced on the reserve of this type of coinage. Since it is absent from these coins, it indicates they was struck before this date. Nine of the coins have an inscription that reads Qianyuan zhongbao [乾元重寶] (heavy treasure of the Qianyuan era) which indicates they were minted from 758 onwards.
