Standardization production of Qi Knives: A comprehensive analysis of the minting remains of knife money unearthed in ancient Linzi in the late Warring states period

Our studies focus on the production background of early standardized coinage in Qi state before Qin empire’s unification of currency. These mold samples have considerable clay content, possibly to limit thermal expansion and enhance casting strength. Slag types include plate slag and ceramic slag attached on blowpipes. The matrix composition of plate slag is characterized by a high content of iron and calcium, with significant quantities of matte (CuPbFeS) and bronze droplets. The matrix composition of ceramic slag exhibits low content of iron and calcium with some copper droplets. It may be inferred that a smelting process is utilized to extract matte from sulfur-containing copper-lead ores, with the addition of tin occurring nearly concurrently. It is also possible to introduce a distinct step that smelting and alloying are totally separated. The lead isotope ratios of slag and mold samples overlap with each other and concentrate in the range with high ²⁰⁷Pb/²⁰⁶Pb ratios. The change of lead resources in Qi knives was synchronized with the change of its alloy composition. We can’t exclude that the lead resources of high ²⁰⁷Pb/²⁰⁶Pb ratios used in Qi state came from local areas, and some uranogenic-rich lead resources might be brought in after Yan state’ s conquest. The above research demonstrates that the production of Qi knives exhibited a significant degree of standardization in terms of molding technology, smelting technology, alloying technology and ore source. The implementation of unified coinage system during the Tian Qi period can be seen as a strategic approach to monopolize the minting rights and foster the growth of the commodities economy.