China Tea Company used to be state-owned, with several tea factories, including four Pu 'er tea factories. Each tea factory has a code name, which is the last tea label produced by this factory. Kunming tea factory code is 1, Menghai tea factory code is 2, Xiaguan tea factory code is 3, and Pu 'er tea factory code is 4. Tea produced by four tea factories all adopt the trademark of China Tea. In the 1980s, the country of tea was liberalized and began to take the market economy. Various tea factories were gradually separated from China Tea Company. Menghai Tea Factory registered Dayi brand trademark in the late 1990s and began to produce Dayi brand Pu 'er tea. Moreover, many changes that China Tea Company has experienced (it also sold trademarks in 2007, which was a bit messy) have now been acquired by COFCO.

7542 still depends on Menghai factory.