South Africa 1931 (14.12.) 4d. rate  cover addressed to Cape Town bearing 3d  air single (Scott # C5; SG86) and 1d (SG75) vertical pair black rubber LUGPOS/GROOT- FONTEIN/AIR MAIL handstamp with GROOT- FONTEIN/ SWA cds below, WINDHOEK 15.12 arrival cds on back