This is a rubber stamp applied in the Netherlands on the reverse of a German postal card paying 30 Pfennig rate in January 1921. Any clue as to its significance?
re: On Postcard from Barmen, Germany, to Netherlands
I think that the rubberstamp placed on the card was just for cataloging the incoming post.
The stamp is from the Haarlem oil factory Gebroeders Waaning-Tilly in Haarlem.
Haarlemer Olie was famous in those days as a medicine.
