The letter was written in Mexiko (May 30th 1846) and sent with the brig "Aguila" from Havana to Spain. There is a manuscript "Por Cadiz" but the applied type of "YNDIAS" mark was not used in Cadiz.
The "YNDIAS" mark was necessary to calculate the correct postage which was collected by the recipient. The type with the slooped "S" was used from 1839-1856 and is known from Santander, Vigo and Bilbao. This lead to the assumption that the brig had to perform quarantine in San Simon (Vigo) before the ship was allowed to travel to Cadiz. The letter was scratched twice with a sharp blade for fumigation.
The recipient had to pay 26 Reales for a letter up to 1,5 ounces from Cuba to Spain.