Princess Diana's famous sheep sweater will be auctioned by Sotheby's after its designers found it in an attic

• The original sheep-print sweater worn by Princess Diana in 1981 will be put up for auction this fall.
• Sotheby's estimates the Warm & Wonderful garment will be listed between $50,000 and $80,000.

One of the most famous pieces of Princess Diana's wardrobe could be yours this fall.

Auction company Sotheby's revealed via Instagram on Sunday that its upcoming Fashion Icons sale will feature the beloved, sheep-print sweater the late British royal wore to one of then-Prince Charles' polo matches in 1981.

Designed by the British brand Warm & Wonderful, the red garment is widely recognized thanks to its vibrant colors, its bold animal print, and its whimsical nature that helped lead Princess Diana to fashion-icon status.

Bidding will open on August 31 and remain open until September 14. Sotheby's estimates that it will be listed between $50,000 and $80,000.

While any garment worn by Princess Diana would be widely admired, this particular piece has a deep history.

According to a press release from Sotheby's, the original sweater was damaged by the princess and sent back to Warm & Wonderful weeks after she first wore it with a request for repair or replacement.

Designers Sally Muir and Joanna Osborne crafted a new one for the royal, and were later thanked by Diana's personal secretary.

The princess wore the second piece on multiple occasions, helping craft her image as a relatable black sheep, no pun intended — something other royals had never done as successfully.

"By combining high-end designer pieces with more attainable everyday apparel, Diana's style led to a wave of imitation
and admiration — which remains steadfast to this day — leaving an indelible mark on the fashion world and solidifying the Princess as an icon in fashion history," Cynthia Houlton, Sotheby's global head of fashion and accessories, said in the press release.

Sotheby's previously listed the most expensive garment of Princess Diana's ever sold: a velvet gown she wore in a royal portrait and in a magazine spread for $604,800 in January.

It wasn't until this year that the original sweater was rediscovered by its original designers in the most unlikely of places, according to Sotheby's.

"This past March, as we were rummaging through the attic searching for an old pattern, we spotted a small box," Muir and Osborne said in the press release. "Inside, tucked away beside a cotton bedspread was Diana's original red sheep sweater from 1981."

"Now, almost four decades later, this one-of-a-kind sheep sweater is ready to make its way into the hands of a fortunate collector," they added.