A meta-stamp celebrating stamps! What follows is my rough translation of a German Wikipedia page, so bear with me…
Stamp Day was the idea of Hans Von Rudolph who, in 1935, though it would be a good idea to something something. The first Stamp Day was in January 1936; the date for Stamp `day has fluctuated over the years. In 1978, stamp day was 12 October. Von Rudolph was a philatelist who documented catalogues of stamps, so I guess I’m a spiritual relation now.
The image shown on the stamp is the sign from the post house in Baden, circa 1825 or 1844, depending which image search you believe.
Here’s a random news story about a German postal worker for you: