5 Zhu ("Western Han" type; filed edge)

The 5 Zhu coin was introduced by Emperor Wu of the Western Han dynasty in 118 BCE to standardize the currency system and curb the proliferation of lightweight, illicit coinage. By centralizing production under the central government, the state aimed to stabilize the economy and consolidate imperial authority across the empire. The design, characterized by a circular shape with a square hole, reflected the traditional Chinese cosmological view of the heavens being round and the earth being square, a motif that would persist in Chinese numismatics for centuries.

These coins were produced through a sand-casting process, often resulting in slight variations in weight and diameter. The 'filed edge' detail mentioned is a common characteristic of Western Han issues, where artisans manually finished the perimeter of the coin to remove excess metal from the casting sprue. While the coinage was initially successful in centralizing economic control, the high volume of production and subsequent economic pressures eventually led to the degradation of casting quality in later periods, yet the 5 Zhu remained a foundational standard of the Han economic legacy.