Unveiling Ming vassal policy through the chemical composition analysis of gold enfeoffment books

The ancestral fief system was a traditional Chinese political practice in which the emperor granted his brothers and sons territories as vassal kings—a process known as enfeoffment—to consolidate national stability. Enfeoffment, a term rooted in feudal governance, refers to the formal act of granting land or titles in exchange for loyalty and service. This system reached its peak during the Ming Dynasty (1368–1644 CE), which introduced specific policies for managing vassal kings. Gold enfeoffment books, physical tokens of this system, reflect the Ming government's stance toward vassal kings. This study employed portable X-ray fluorescence spectroscopy to analyse twelve gold books given by the Ming royal court to the Rong vassal state to reveal the diachronic change of their compositional characteristics. These books are all found to be ternary alloys of Au, Ag, and Cu but show a significant declining trend in their Au content from the Hongzhi to the Chongzhen eras (1501–1634 CE). Two major compositional changes of the gold books coincided with the promulgation of the "Regulations of Clans and vassals" during the Jiajing era (1522–1566 CE) and the implementation of the "Fixed Benefits System" during the Wanli era (1573 -1620 CE). The material characteristics of the gold books evidenced the rise, sustenance, and eventual collapse of the ancestral fief system during the Ming dynasty.