The pregnant royal, who is expecting her third child in April, was pictured arriving with husband Prince William and brother-in-law Prince Harry at Windsor Castle on Monday to celebrate the Queen, 91, and Prince Philip‘s 70th wedding anniversary.
The four-strand pearl choker with central diamond clasp, worn by the Queen during the 1980s and 1990s, was commissioned using a collection of cultured pearls given to her by the Japanese government.
Princess Diana borrowed the piece to wear at a state banquet for the Netherlands in 1982.S
And the necklace was not the only accessory that was passed down to the Duchess.
On Monday, the mother-to-be also wore the Collingwood pearl and diamond earrings, which were a wedding present to the late Princess of Wales and kept in her private collection. Middleton previously wore them in July during the state banquet for the visiting Spanish royals.
The royal opted for her favorite black Diane von Furstenberg Zarita lace gown that she wore earlier this month during a Kensington Palace gala. She also wore the dress when she was pregnant with Princess Charlotte in November 2014. And a month later, she wore the black evening gown again to a friend’s wedding in London.
This article originally appeared on PEOPLE.