"Chen" is Beichen, which is also the North Star. The emperor sits facing south, so Beichen also refers to the feudal emperor.
"Han" originally refers to feathers, and later refers to brush, ink, articles, calligraphy and painting, seals, letters and other "Chen Han", that is, the calligraphy of Emperor Qianlong.
Not only Emperor Qianlong, Emperor Kangxi and Yong Zhengdi have similar seals of "Kangxi Chen Han" and "Yongzheng Chen Han". The imperial pen of the ancient emperor was generally unsigned, but the word "imperial pen" was written in calligraphy or stamped with the imperial seal. Hope to adopt.