The royal family has released a new photograph of Prince Philip and Queen Elizabeth II in celebration of the duke’s 99th birthday on June 10.

The image, taken at Windsor Castle on June 1, shows the Prince donning a Household Division tie and the Queen wearing a dress by Angela Kelly and a historic brooch.

Dating back to 1911, the Cullinan V brooch features an 18-8-carat heart-shaped diamond at its centre with pave-set border of smaller diamonds.

The centre stone is one of those cut from the famous 3,106-carat Cullinan, the largest diamond ever discovered. Other stones from the 621g diamond – found near Pretoria in South Africa in 1905 – were set on other royal jewellery pieces, including the Imperial State Crown and the Sovereign’s Sceptre.

The Cullinan V was first owned by the Queen’s grandmother Queen Mary, who wore the brooch as part of the suite of jewelleries made for the Delhi Durbar in 1911.

Elizabeth later inherited the piece in 1953 and has since featured it as part of her outfit on many occasions. She was last seen wearing the brooch during the wedding of Princess Eugenie and Jack Brooksbank’s wedding at St George’s Chapel in October 2018.

This article originally appeared on Over60.