the QSL Card was designed by Dutch DXer Guido Schotmans and there were only 100 made. I have one and two or three other German DXers also received one. When I visited the RTZ last year they still had plenty of them. It seems they only send them out to selected people ;-)
RTZ remains a hard to QSL station. Good luck!
Dénia/Spain (38.50N 00.04E)