During the 1970s, promotional copies of albums released by or distributed through Warner Bros. Records (or one of the company’s sublabels) would sometimes feature this hot pink sticker stuck on their cover. Doing a few searches on Discogs, it appears that these stickers were primarily used from 1972 to 1979.
One variation of the sticker featured the WEA logo in yellow. It seems this version was used into the very early 1980s. The pictured example is from a copy of The Rolling Stones’ Sucking in the Seventies (released March 1981).