Southern Song dynasty coinage

The Southern Song dynasty was an era of the Song dynasty after Kaifeng was captured by the Jurchen-led Jin dynasty in 1127. The government of the Song was forced to establish a new capital city at Lin'an (present day Hangzhou) which wasn't near any sources of copper so the quality of the cash coins produced under the Southern Song significantly deteriorated compared to the cast copper-alloy cash coins of the Northern Song dynasty.

Source: Wikipedia — Southern Song dynasty coinage (CC BY-SA 4.0)