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Princess Anne, the hardest-working member of the royal family, recently made an appearance at a gala dinner supporting the Eric Liddell 100, which celebrates the life and times of the Scottish athlete and his historic performance at the 1924 Olympic Games. While her vintage dress may have gotten the majority of the spotlight—the Princess Royal wore a Frank Usher dress from the 1960s—her sapphire-and-pearl brooch was a touching tribute to the late Queen Elizabeth.

According to experts from U.K. retailer Steven Stone, Anne wore one of Elizabeth’s favorite pieces. The piece first entered the royal collection in 1866, when Alexandra, Princess of Wales at the time, purchased it as a wedding present for her sister, Empress Maria Feodorovna. Later, Queen Mary acquired the brooch and it was passed down to Queen Elizabeth and now, Anne.

The brooch features a sapphire surrounded by two rows of diamonds and a distinctive drop-pearl embellishment.

“The eye-catching piece features a sugarloaf cabochon sapphire encircled by two rows of diamonds and has a removable pearl droplet that hangs delicately underneath,” jewelry expert Maxwell Stone explained. “The incredible sapphire and intricate diamond detailing would give this piece an estimated value of over £500,000 [approximately $648,880].”

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Stone expanded on the piece’s history and mentioned that Queen Elizabeth wore it on some of her most memorable royal tours.

“It’s heartwarming to see Princess Anne paying tribute to her late mother through her jewelry—particularly such a historic piece. The brooch originally belonged to Empress Maria Feodorovna and was reportedly bought by Queen Mary,” Stone added. “When Queen Elizabeth II inherited the throne, her grandmother’s brooch was passed down to her and she wore it multiple times over the years—making it one of the most popular pieces from the late monarch’s brooch collection.”

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Anne is a patron of the Eric Liddell 100 and at this year’s event, she presented an award while wearing the dramatic backless dress. The organization works to inspire young people to make a “positive impact on their community” and celebrate Liddell’s legacy, values, and integrity.