50.000 Mark airmail stamps in the incorrect perforation 16er - sheet, containing 15 stamps 5 million / 50.000 M without overprint of the new value as well the printing error 5 million / 10.000 M without overprint of the new value. The very scarce block piece is genuine and mint never hinged, the defective or badly placed perforation is on inaccurate attachment in of the perforating machine to lead back, photo expertize Dr. Oechsner BPP.