According to Chan Kam Pong's "First steps to Chinese Pu erh Tea", he explained "In order to identify different kinds of puerh tea products in the tea factory, trading codes were introduced after a Puerh tea industrial meeting being held by Yunnan provincial branch in 1976. It was resolved that Kunming Tea Factory, Menghai Tea Factory and Xiaguan Tea Factory should enlarge their productions of Ripe puerh tea and in the meantime specific trading codes should be assigned to different qualities of products for easy identification. The code number for tea cakes were assigned 4 digits. The entire code represents the formula of a tea cake'
There you have it. The 4 digits is a recipe of a puerh tea cake. Look at the 1st two pix, you see 8808 in the 1st pix and 0532 in the 2nd pix. That is the recipe code. The 1st 2 digits represents the invention of the recipe. Thus 8808 means the recipe was first used in 1988, while the 2nd pix 0532 means 2005. The 3rd digit will indicate the tea leaf grade used. The range from 0-9 used to assess tea leafs, finer leafs are of a lower number. The grading of leafs used in the formula of puerh tea is little subjective as such grades do not take into account the area or season (spring summer...).of the leaf harvested. The age and mixture of the tea leaves cannot be determined in this aspect. The last digit represents the production house where the tea formula originated. 1,2,3 represents Kunming, Menghai and Xiaguan respectively. Haiwan Tea factory was given the code 8.
As these 4 digits are not exclusive or trademarked to the tea factory, you see such numbers being used in among the different factories of puerh tea.
You do sometimes see an addition 3 digits on some cakes like 801 in both pix. Well just look at the back of the wrapper (3rd pix) to see the production year. In this case is 2008. This means 801 meant the 1st production of this recipe for the year 2008. If it is 803, it will indicate the 3rd production run of this recipe for the year 2008. In general, a production run is about 100 baskets (8400 tea cakes).