At what point does a piece of clothing, an accessory, or an ensemble move beyond “chic, “pretty,” or “beautiful” to become “iconic”? It’s hard to know. Thinking of Princess Diana, for instance, there are ballgowns aplenty from which to choose, and yet Sotheby’s has picked a simple sweater: her instantly recognizable and widely analyzed 1981 “Sheep Jumper.” This red pullover sweater covered with white sheep—and one black sheep, i.e Diana!—was so beloved that Rowing Blazers recreated it in 2020. Recently found in an attic, the original knit is heading to the auction block, where bidding for the humble piece of royal history opens online on August 31 and ends September 14; the estimate is $50,000 to $80,000. Other “iconic” items in the auction of 10 pieces? Sarah Jessica Parker’s blue Bird of Paradise headpiece from Sex and the City; Michelle Obama’s black 1950s Norman Norell, worn in 2010; and Kate Winslet’s green Givenchy mermaid gown, designed by Alexander McQueen and worn to the Academy Awards in 1998. All are on view from September 7 to 13. —Lucy Horowitz