Grew up in West Germany when the Demoscene was at it's height, but never heard of "pink PLK cards". Could you give a hint what that is?
EDIT: Found it "Postlagerkarte"[1], I have heard that term before, but never was aware what it was. It feels strange that at a time you could do things easily, legally and anonymously, all at the same time. As a minor, at that. Let alone anonymously sending things to strangers. Admittedly I miss that world more than the Demoscene.