In fact, this seal with the word "囧" has an extra frame outside the character "公". In the paintings with this seal, there is another seal script "Xin Gong Treasures" under each seal with the word "公" seal. In the past, there was a tradition in the field of calligraphy and painting collection. Collectors would add their own seals to the original works. In the Qing Dynasty, there was a master of calligraphy and painting connoisseur named Geng Zhaozhong, also known as Xingong. Many ancient paintings and calligraphy works circulated in the world today have his two seals, so they are relatively common. Personally, I think this is just a coincidence, just a private collection stamp.
Geng Zhaozhong [Qing Dynasty] (1640-1686) was born in Zhenghuang Banner of the Han Army. Originally from Shandong, he came to Gaizhou, Liaodong (now Gaiping, Liaoning). The second son of Ji Mao. He was appointed the Taibao of the Jin Crown Prince by Duo Luo'e. His posthumous title is Qinxi. Good at articles, crafts, and identification. As well as calligraphy, painting, qin, chess, Xiao, Zhu, medicine, flute, Pubo, etc., he is often excellent. The famous traces of the Song and Yuan Dynasties that are circulated in this world all have the seal of the Geng family on them. He died at the age of forty-seven.