Puerh History - Pu-erh.Net

„Yunnan Tea Company standardized the trade number for Pu Erh Tea in 1976 for the purpose of export. Each bingcha has 4 digits: the first 2 digits indicate the manufacturing year, the third digit indicates the leaf grade, the last digit indicates the tea factory (e.g. Kun-Ming 1, Meng-Hai 2, Xia-Guan 3, Pu Erh 4). The loose-leaf tea has 5 digits with the third and fourth indicating the class level of raw materials. Examples of early trade numbers for Puerh Tea are 7452, 7562, 7572, 75671, 76563.“

„Smokiness
The art of making tea from ancient tea trees is very old. Hand-roasting is not easily mastered. Any slight error will influence the taste of the tea. Smokiness or yan wei is one example but it should be distinguished from a burned flavour which is described as hu wei. The latter, typically arises when tea is not well roasted and is, unfortunately, not uncommon. Yan wei or smokiness is caused by oven drying. “