Nearly all of the stamps issued for the Azores were stamps of Portugal

Portugal

Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

, overprint

Overprint

An overprint is an additional layer of text or graphics added to the face of a postage stamp or banknote after it has been printed. Post offices most often use overprints for internal administrative purposes such as accounting but they are also employed in public mail...

ed "AÇORES", of which the first appeared in 1868, continuing through 1930; after 1930, Portuguese stamps were used unmodified. The exceptions were the Vasco da Gama

Vasco da Gama

Vasco da Gama, 1st Count of Vidigueira was a Portuguese explorer, one of the most successful in the Age of Discovery and the commander of the first ships to sail directly from Europe to India...

 issue of 1898, the King Carlos

Carlos I of Portugal

-Assassination:On 1 February 1908 the royal family returned from the palace of Vila Viçosa to Lisbon. They travelled by train to Barreiro and, from there, they took a steamer to cross the Tagus River and disembarked at Cais do Sodré in central Lisbon. On their way to the royal palace, the open...

 issue of 1906, and the King Manuel

Manuel II of Portugal

Manuel II , named Manuel Maria Filipe Carlos Amélio Luís Miguel Rafael Gabriel Gonzaga Francisco de Assis Eugénio de Bragança Orleães Sabóia e Saxe-Coburgo-Gotha — , was the last King of Portugal from 1908 to 1910, ascending the throne after the assassination of his father and elder brother Manuel...

 issue and Manual revolutionary overprints of 1910.

Angra, Horta & Ponta Delgada

Between 1892 and 1906, the three administrative districts of the Azores had stamps issued inscribed with their names: Angra, Horta, and Ponta Delgada. The designs were identical to those of the regular Portuguese stamps, which were inscribed "CONTINENTE" to distinguish them, and the colors generally the same, with some lighter or darker.

Modern issues

On 2 January 1980, the use of separate stamps for the Azores (and Madeira

Madeira

Madeira is a Portuguese archipelago that lies between and , just under 400 km north of Tenerife, Canary Islands, in the north Atlantic Ocean and an outermost region of the European Union...

) was revived. The modern stamps are inscribed both "PORTUGAL" and "AÇORES". The stamps have no special purpose beyond the expression of local pride; all are sold and valid in Portugal. About 5-10 are issued each year, generally with themes relating to the Azores.

Sources

• Stanley Gibbons Ltd: various catalogues
• Encyclopaedia of Postal History
• Rossiter, Stuart
  Stuart Rossiter
  Percival "Stuart" Bryce Rossiter was a renowned British philatelist and postal historian who wrote extensively about British postal history and postage stamps of British colonies in Africa and was actively involved in numerous philatelic institutions...
  
  & John Flower. The Stamp Atlas. London: Macdonald, 1986. ISBN 0356108627