On June 25, 1997, just months before Princess Diana’s death in August, dozens of her dresses were auctioned off at Christie’s in New York. Now, some of her handwritten letters regarding that event are hitting the auction block.

Princess Diana wrote the letters to her friend Elizabeth Tilberis, editor-in-chief of Harper’s Bazaar at the time, both leading up to and after the auction.

“The news of the auction came out far too early & it’s due to be announced next week from Christies! [sic],” she penned on February 25, 1997. “It’s been quite an event sorting out the frocks—memories flooding back & some excellent ones too!”

Princess Diana's letter to Elizabeth Tilberis from February 25, 1997.Swann Auction Galleries

She ended up choosing a total of 79 garments, including several of her most memorable ones. According to The New York Times, the slinky velvet gown she wore while dancing with John Travolta at a White House dinner in 1985 fetched an impressive $222,500, and what she called her “Elvis dress”—a pearl-encrusted white number with a matching, high-necked bolero jacket—sold for $151,000. Overall, the auction raised a staggering $3.25 million, which was donated to the Royal Marsden Hospital Cancer Fund and the AIDS Crisis Trust.

“It was stunning the amount made by the auction last week,” she wrote to Tilberis on July 1. “How typical of the Americans to be so totally generous. I can always rely on them!”

The personal letters are estimated to sell somewhere in the region of $6000 to $9000, but they’re not the only Princess Diana items in the auction. Swann Auction Galleries is also offering an auction catalog signed by Princess Diana, Tilberis’s paddle registration card, Princess Diana’s signed menu from a 1990 benefit dinner held by the British Deaf Association, and a 1996 Christmas card with a photograph of Princes William and Harry with their cousins, Princesses Beatrice and Eugenie.

A Christmas card from 1996 featuring the young Princes William and Harry with their cousins, Princesses Beatrice and Eugenie.Swann Auction Galleries

In addition to the royal family memorabilia, the auction—which takes place on Thursday, February 20—will include rare first editions of several Jane Austen novels, too.