Sorting these covers by decade
Watchmen by decade
Alan Moore and 3 others
20 covers from 29 printings with a known year, 2020s back to 1980s
2020s
2 covers · 2 publishers, DC Comics and ECC Ediciones among them
2010s
5 covers · 2 of 9 printings say hardcover · 7 publishers, DC Comics and dc among them · 3 languages
2000s
7 covers · 5 of 12 printings say paperback · 7 publishers, DC Comics and Planeta DeAgostini among them · 4 languages
1980s
4 covers · 7 of 13 printings say paperback · 6 publishers, DC Comics and Titan Books Ltd among them
No year on record
2 covers
Covers from Open Library, each in the decade of the earliest printing that carries it. What the catalogues never scanned is missing here too. See the whole wall.