Cauca, Colombian state, 1879 "Arms of Choco" 5c black, used on cover to Rio Sucio tied by manuscript cancel "QUIBDO 1881" The envelope with some faults at top left otherwise in fine condition for this primitive issue. ONLY THREE COVERS OF THIS MAJOR COLOMBIA RARITY ARE KNOWN (two single frankings and a cover with several stamps missing). CERTAINLY ONE OF THE RAREST NUMBER ONES OF THE WORLD ON COVER. Certificates Roger Calves (2008), BPA (2011) and Brian Moorhouse (2012). Michel 1, Yvert 1A on cover 75.000 EUR. (Image)