 The Sinan shipwreck, which was a ship from Ningbo to Hakata that sank off the Korean coast in the year 1323, carried some 8,000 strings of cash coins, which weighed about 26,775 kg.As the Chinese coins were not in sufficient number as trade and economy expanded, local Japanese imitations of Chinese coins were made from the 14th century, especially imitations of Ming coins, with inscribed names identical to those of contemporary Chinese coins.These coins had a very low value compared to Chinese coins, and several of them had to be exchanged for just one Chinese coin.