Although iron coins were also minted during the period of the Sung Dynasty (in marginal areas such as the Sichuan Province and the Shan Xi Province, the possession and use of copper coins were totally banned to prevent copper from going out to the Liao Dynasty and Xi Xia, and instead, people were forced to use iron coins), generally, Sung currency means copper coins which were the overwhelming majority.
また、宋代には鉄銭も鋳造された（辺境部である四川省・陝西省において、遼・西夏への銅の流出を防止するために、銅銭の所有・使用一切を禁じられて代わりに鉄銭が強制的に流通させられたため）が、一般的には、圧倒的に多い銅銭のことを指して宋銭と呼んでいる。