The world's oldest coin minting workshop, dating back about 2,500 years, has been discovered in Central China's Henan province. Using radiocarbon dating, Chinese archaeologists have confirmed that a bronze casting workshop in the ruins of Guanzhuang in Xingyang, in the western part of the provincial capital Zhengzhou, began to mint standardized metal money around 640-550 BC, making it the earliest known coin making workshop in the world. During further excavation, four types of relics related to coin manufacturing were unearthed at the site, including finished coins, used and unused coin molds, and outer molds, said Han Guohe, an archaeology professor at Zhengzhou University. Archaeologists have also uncovered several pits where large quantities of bronze casting waste were dumped, with two finished metal coins found in one of the pits.