These packs come from a box authenticated by Baseball Card Exchange.
1981 Topps is a 726-card set released as a single series. This was the first year since 1955 in which Topps had competition, and is generally considered to be the beginning of the "Modern Era" of baseball cards.
In 1981, Topps introduced three statistical categories to the backs of cards - Slugging Percentage (SLG), Walks (BB), and Strikeouts (SO). 1981 also saw the return of Stolen Bases (SB) which has been absent since 1971.