1912 Rio Grande do Norte ("Thesouro") Carmine & black, Center inverted, unused block of four with "Waterlow Brothers & Layton, Lim'd Birchin Lane, Londres, Inglaterra" imprint in margin, without gum as issued, very fine, Bileski reports "a block of 12 was in the Baron Ferrari collection, I purchased it intact and separated it into eight singles and this one imprint block, feel certain it is unique"