When is the bottom porcelain of Lujiajun kiln?

Lujiajun Kiln started at 1870. Due to the war in history, the firing technique of Jun porcelain was basically lost in the early Qing Dynasty. In the fifth year of Guangxu in Qing Dynasty, Lu Zhentai, a kiln worker in Shenhou Town, was determined to restore Jun porcelain, and successfully fired "Yu Gong Jiu Ding" on 1902, which became the birthday gift of Empress Dowager Cixi on her 60th birthday. Later, on 19 15, she represented the country in Panama World Expo. Therefore, Lujiajun Kiln is a modern porcelain and a very successful porcelain in Jun Kiln. thank you