The Azores are a group of islands far off the Portuguese coast in the north Atlantic ocean; they are a part of Portugal and use Portuguese stamps. The name of the islands, as rendered in Portuguese on all stamps, is Açores.
In 1868, however, Portuguese stamps with special overprints were used in the Azores. This approach continued for decades; only very few stamps (and postage due stamps and other specialty items) actually had “Açores” printed on them.
There were three regions within the Azores, oddly, that did have their own stamps made from 1892 until 1906: Angra, Horta, and Ponta Delgado.
In 1930, the stamps of Portugal without any special overprints were used. This went on until 1980, when stamps printed “Açores” were once again issued. These Azores stamps also say “Portugal”, and they are technically Portuguese stamps, valid anywhere in that country as well as the Azores themselves. There are several special collectible Azores stamps, maxicards, et cetera in the modern era from the Azores. See subcategories for more.
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Check the current Azores postage stamps for sale here; the selection changes every day.