actually the question was in the specific address from which the UID for STM8L051 begins. experimentally found out on three controllers. the first from one batch and the last two from another batch. The UID for STM8L051 is located in memory at 0x4926, this can be seen in the picture below.
by analogy with the datasheet on STM8S105x4/6 page 50 Unique ID, you can determine how the UID for STM8L051 is formed. see the picture below.