Daoist ordination certificate, Putian.
Source: Kenneth Dean, Taoist ritual and popular cults of southeast China.
In the spirit of I’m sorry I haven’t a clue…
Further to Speaking from the heart, where I noted the somewhat elaborate definition of the term dundian, here’s another fine definition—ironically, from the Chinese-Chinese dictionary of my Daoist master Li Manshan, no less, which we consulted when I mentioned the term lu 籙, Daoist “registers” (lengthy hereditary titles bestowing the authority to conduct rituals), unfamiliar to him (my translation):
a superstitious thing that Daoists use to trick people
Hmm. Li Manshan shrugs, and we both giggle.