<treasure no.645> This is an example of yongjun—a king’s jar with dragon design—adorned in underglaze iron. A yongjun’s designs were typically drawn in underglaze blue. The early 17th century, when white porcelain yongjun in underglaze iron were produced, took place in the aftermath of war, and those yongjun in underglaze iron were produced to solve the shortage of white porcelain yongjun in underglaze blue. Relevant evidence was identified at the royal kilns, whose operational period is presumed to have been the early and mid-17th century, where jar shards with a dragon design in underglaze iron were found