The Queen wears the brooch at the Canadian Museum of Nature in Ottawa, June 2010 (Chris Jackson/Getty Images)

You know you have a serious amount of charisma when multiple people who are not family members leave you glittering jewels in their wills. Such was the luck of the Queen Mum, who famously received the gigantic Greville jewel bequest from a family friend; even better, she also inherited today’s piece, the Courtauld Thomson Scallop-Shell Brooch, from a loyal subject.

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The brooch, which features a shell motif in diamonds studded with a single round pearl, was made in 1919 in London by the Goldsmiths and Silversmiths Co., Ltd. It was designed in part by Sir Courtauld Thomson, who was the son of a famous Scottish inventor. His sister, the writer Winifred Hope Thomson, ended up with the piece, and she was the one who left it to the Queen Mum in 1944.

The Queen Mother wears the brooch in London for the Trooping the Colour carriage procession, June 2000 (SUNDAY MIRROR/AFP/Getty Images)

According to Hugh Roberts, Thomson noted that she willed the brooch to the Queen Mum “as a mark of respect and profound admiration.” She also indicated that she wanted it to be a brooch that was passed from queen to queen in Britain.

The Queen Mother (with Prince Charles) wears the brooch on her 100th birthday, 4 August 2000 (ADRIAN DENNIS/AFP/Getty Images)

The Queen Mum wore the gorgeous brooch throughout her lifetime. It was clearly a valued possession, because she chose to wear it on her 100th birthday in August 2000. When she died two years later, the brooch was inherited by her daughter, Queen Elizabeth II.

The Queen wears the brooch at the wedding of Zara Phillips and Mike Tindall in Edinburgh, July 2011 (BEN STANSALL/AFP/Getty Images)

The Queen has been wearing the scallop-shell brooch more and more in recent years. She even selected it for the wedding of her eldest granddaughter, Zara Phillips, in 2011.

The Queen wears the brooch for the unveiling of a statue of the Queen Mother on the Mall near Buckingham Palace, February 2009 (KIRSTY WIGGLESWORTH/AFP/Getty Images)

Appropriately, the Queen has also worn it for important events related to her mother, including a memorial service marking ten years since the Queen Mother’s death and the unveiling of her statue on the Mall.

The Queen Mother wears the Duchess of Teck’s Flower Brooch at Dover Castle (Wikimedia Commons)

When you look at old photographs of the Queen Mother, one piece of jewelry in particular crops up often among her daytime attire: a diamond flower brooch with four pendants and a detachable diamond chain. It was one of the Queen Mum’s wedding gifts, but its history goes back even further than that.

An 1856 daguerreotype by Antoine Claudet of Queen Victoria with her aunt, Princess Mary, Duchess of Gloucster, and two of her children, the Prince of Wales and Princess Alice (Wikimedia Commons)

We know for sure that this brooch once belonged to Queen Mary’s mother, Princess Mary Adelaide, Duchess of Teck. It’s definitely a nineteenth-century creation, possibly created by Garrard. But Hugh Roberts speculates in The Queen’s Diamonds that its history is even longer. He posits that the brooch once belonged to Princess Mary, Duchess of Gloucester.

Princess Mary Adelaide, Duchess of Teck depicted in a bejeweled portrait by Hermann Schmiechen, ca. 1882; Mary Adelaide’s jewelry includes the Teck Ears of Wheat Tiara and the Teck Diamond Hoop Necklace (Wikimedia Commons)

Princess Mary was one of the fifteen children of King George III and Queen Charlotte. She married her first cousin, the Duke of Gloucester and Edinburgh, in 1816. She didn’t have any children of her own, but she was close to two of her royal nieces: Queen Victoria (the daughter of the Duke of Kent) and Princess Mary Adelaide, Duchess of Teck (the daughter of the Duke of Cambridge). When Princess Mary died in 1857, she bequeathed a collection of jewelry to Princess Mary Adelaide. We know for sure that the bequest included the Gloucester Pendant Earrings; if Roberts is correct, it may also have included this brooch.

Prince Adolphus of Teck and Lady Margaret Grosvenor on their wedding day; the bridesmaids were Lady Mary Grosvenor and Lady Helen Grosvenor (half-sisters of the bride), as well as four of the bride’s nieces, Lady Constance Grosvenor, Lady Millicent Grosvenor, Lady Beatrice Butler, and the Hon. Lilah Cavendish

Regardless, the brooch was definitely in Princess Mary Adelaide’s collection by the time of her death in 1897. The duchess died without a will, and her jewels were divided up among her children. This brooch was inherited by her eldest son, Prince Adolphus. (He would later inherit his father’s title, becoming the Duke of Teck. After the outbreak of World War I, however, Adolphus renounced his German titles and was created the Marquess of Cambridge by his brother-in-law, King George V.)

At some point, the brooch changed hands between the Teck children. By 1923, it was in the collection of Prince Adolphus’s elder sister, Queen Mary. That year, she handed over the brooch to her second son, the Duke of York, so that he could give it to his new bride, Elizabeth Bowes-Lyon. The Yorks would eventually become King George VI and Queen Elizabeth; she would be better known later as the Queen Mother. The Queen Mum wore the brooch from the very start of her marriage, posing in the piece with her lotus flower tiara in the 1920s. You can see it positioned on the strap of her dress in the photograph above.

The Queen Mother wears the brooch at Dover Castle in Kent (Wikimedia Commons)

And she continued to wear the piece throughout her life. You can often spot it in photos, pinned high on her shoulder. Photographer Allan Warren snapped her wearing the brooch during an engagement at Dover Castle in Kent. You’ll note that she’s also wearing an additional badge (a backwards “s” bisected by an oar) below the brooch’s central pendant.

She also wore the brooch with her gala jewels at evening events, as she did during this trip to the theater in 1985. (You may notice that she’s also wearing the Duchess of Cornwall’s engagement ring.)

JOHNNY EGGITT/AFP/Getty Images

Near the end of her life, the Queen Mother’s milestone birthdays were celebrated with public appearances. Above, she wears the brooch for the celebrations of her 89th birthday in August 1989.

When the Queen Mum died in 2002, her jewels were inherited by her daughter, Queen Elizabeth II. The brooch is in the Queen’s collection today, but although Roberts says she has worn it “on occasions” since 2002, it seems that the only public appearance of the jewel so far has been in a portrait taken by her former brother-in-law, Lord Snowdon. Appropriately, the photograph was printed on the cover of the Radio Times issue celebrating the BBC’s Diamond Jubilee documentary, The Diamond Queen. Nothing like a major heirloom diamond brooch to go along with the theme!