An iconic red sweater worn by the young Princess Diana, featuring a flock of white sheep with a single black sheep, is set to be auctioned at Sotheby's in September. The whimsical wool jumper is expected to fetch over $50,000 in the Fashion Icons sale.

The sweater gained notoriety after Diana, then Lady Diana Spencer, was photographed wearing it at a polo match in June 1981, shortly after her engagement to Prince Charles. This appearance cemented her burgeoning status as a fashion icon and brought significant attention to the sweater's designers, Sally Muir and Joanna Osborne, founders of the knitwear label Warm & Wonderful.

Following the polo match, Buckingham Palace contacted Muir and Osborne, explaining that the sweater had been damaged and inquiring about repair or replacement. The damaged original, believed to have been snagged by Diana's engagement ring, was returned, and a new sweater was sent to the princess. Diana was later seen wearing the replacement sweater in 1983.

The 'black sheep' motif has led to speculation that Diana identified with it, feeling like an outsider within the royal family. This connection was further highlighted by actress Emma Corrin, who wore a replica of the sweater while portraying Diana in the fourth season of "The Crown."

Warm & Wonderful continues to produce a cotton version of the iconic design. The original wool sweater was recently rediscovered by Osborne, tucked away in an attic. Sotheby’s global head of fashion and accessories, Cynthia Houlton, described the piece as exceptionally well-preserved and evocative of Diana's grace, charm, and fashion sense.

The sweater will be displayed at Sotheby's New York showroom before the online bidding, which opens on August 31st and concludes on September 14th. The estimated price ranges from $50,000 to $80,000. This auction follows the record-breaking sale of a Victor Edelstein gown worn by Diana, which sold for over $600,000 earlier this year.