1922 15C on 10C Lake postal stationery card showing the river Congo „68. Les rapides du Congo à sa sortie du Stanley-Pool“, with VERY RARE VARIETY: TRIPLE SURCHARGE „30/15/15“ from Elisabethville to Brussels. The 10c postal card was first overprinted with the 30c handstamp in order to change into a 30c UPU postcard rate, later this was changed by a 15c surcharge (twice) which made the postal card usable for the Belgium rate. PROBABLY UNIQUE COMMERCIALLY USED. Very fine. Certificate Van der Marcken