e-QSL from Radio WDR “Radio from the Bottom of the Sea”

An e-QSL from Radio WDR. No no the Westdeutscher Rundfunk, but Radio WDR on 5800 kHz, a Free Radio station from the Netherlands. One of their slogans is “Radio from the Bottom of the Sea”. Based on their QSL their location is in the Noordoostpolder which until 1942 was indeed the bottom of the Zuiderzee.