I was cleaning my attic this weekend and while vacuuming the floor out from below an old vinyl floor section emerged this mysterious pin.
Königsstuhl also known as "Kings Chair"
The text on the pin reads “Königsstuhl” which translates to “King’s Chair”. There are several references to this term on Google, one of which is a park founded in 1990 with the same name. Considering the age of our house and the coloring of the pin I believe this is much, much older.

