Several tons of copper coins dating to the Song Dynasty (960-1279 CE) were found recently in an ancient kiln in northwest China’s Shaanxi Province. The coins were strung into ropes through a center hole. (photos)
Millions of such coins were minted during the era. "The variations in calligraphy style, position of the writing relative to the rims, dimensions and styles of the inner and outer rims, and the size of the centre holes, were used to denote mint location, workshop or furnace, and casting period (often more than one per year)."