Sotheby’s has revealed the full contents of its inaugural Fashion Icons sale. The sale, which opens for bidding on Aug. 31 and closes on Sept. 14, is looking like a royal affair.

The auction house has revealed they are offering one of Diana’s most renowned pieces: her 1985 Murray Arbeid gown that she donned to Prince Edward’s 21st birthday party, a themed event titled “A Midsummer Night’s Ball,” held at Windsor Castle’s royal residence on June 1985.

Like many of Diana’s most famous looks, the gown made headline news for days, notably because another guest in attendance wore the same dress. The guest in question was Natasha Fairweather.

Diana wore the dress on more than one occasion, and it turned into one of her defining style moments during her years in the public eye.

The auction house previously revealed it also is offering another of Diana, Princess of Wales’ most famous looks; her viral red and white wool sheep sweater that she wore in June 1981 at one of Prince Charles’ summer polo matches.

“The entire Fashion Icons sale is about one-of-a-kind pieces that reflect various eras of fashion,” said Cynthia Houlton, Sotheby’s global head of fashion and accessories. “Princess Diana is one of the greatest representatives of fashion of her time, so that’s someone we would want to include. She originally sold the dress for charity, and now we are happy it has come to us.”

In addition to Princess Diana’s items, Sarah Jessica Parker’s vintage taxidermy Bird of Paradise headpiece from “Sex and the City: The Movie” is part of the auction. The headpiece was famously worn in the scene where Carrie and Mr. Big go to get married, but Big stands her up at the altar leaving her humiliated. The sale will also include Michelle Obama’s Norman Norell lace dress, Kate Winslet’s Alexander McQueen gown from the 1998 Oscars and Madonna’s lace veil from Vanity Fair’s first Icons issue photo shoot.