I examined 10 inscription blocks and 10 singles (all mint) and do not have your example.
I have a couple examples of heavier diagonal lines running under the E of POSTES.
There are several differences between your two stamps.
The smaller differences are understandable, such as the dots [blue , orange and green arrows], but the wavy lines and the single ghost line in the red box and the irregular lines in the yellow box on the branch are interesting. The water lines are all wavy in one stamp, but all straight in the other.