This issue depicts windmills from several regions of Portugal. The type of windmill on São Miguel is probably due to the Flemish influence in the Azores. The stamps are printed on the back with a description in English, French and Portuguese.
The stamps were designed by Cândido Costa Pinto, lithographed by the Mint on enamelled paper sheets of 10×10 stamps with perforation 13½, and circulated from 24 February 1971 to 31 December 1983.
- David Sayers, Windmills – Moinhos dos Açores, accessed 31 January 2015