1 Cash - Anonymous Kaiyuan Tongbao, iron

The Kaiyuan Tongbao series, launched in 621 under Tang Taizong's predecessor Gaozu, became the template for Chinese cash coinage for the next twelve centuries — its format so dominant that subsequent dynasties largely abandoned naming coins after reign periods for generations. Iron-cast examples proliferated during the mid-to-late Tang as copper shortages, driven by Buddhist temple bell-casting and an insatiable demand for bronze vessels, pushed provincial mints to substitute cheaper metals. These iron issues circulated primarily in inland and northern regions where copper coin supply was tightest.

Hartill 14.10 specimens are notably prone to corrosion, and heavily encrusted survivors are the rule rather than the exception.