1861, Cuban stamp used in Spain, 1 Real, type I wmk, on mourning letter, from ALGECIRAS (Spain) via Gibraltar to JEREZ de la Frontera, tied with ALGECIRAS 27 Mar 61, reverse with dispatch ALGECIRAS and arrival cancel JEREZ 29 MAR 61, it is the ONLY known example of a letter circulating within Spain as internal mail by using a CUBAN stamp from the first issue 1855, UNIQUE rarity, very fresh and attractive, VF-XF! Estimate 4.000€. (Image)