At the royal palace in Darmstadt at Christmas, more than a century ago, Grand Duke Ernst Ludwig of Hesse and by Rhine snuck a very special present under the tree for his wife, Grand Duchess Eleonore: a unique, lovely tiara made of diamonds, turquoises, and moonstones. The Art Nouveau jewel has a fascinating backstory, with sentimental links to the family’s history and the artistic world of Darmstadt.

Grand Duke Ernst—or Ernie, as his family called him—had plenty of reasons to celebrate the holiday with an extra-special present for Christmas 1905. The past year had turned his life around completely. Grand Duchess Eleonore (who was nicknamed “Onor” by those closest to her) was his second wife; he had previously been married to his first cousin, Princess Victoria Melita of Saxe-Coburg and Gotha. Their marriage had been a total mismatch, and the couple were unhappy almost from the start. Divorce was a relatively rare phenomenon for royal couples in those days, and their shared grandmother, Queen Victoria, was adamantly against the end of the marriage. The marriage had produced one child: a daughter, Princess Elisabeth, who was deeply loved by both her parents but was particularly close to her father. After Queen Victoria’s death in 1901, the couple were finally divorced, and they shared custody of their daughter. But tragically, the little princess died of typhoid at the age of eight in 1903. Ernie was devastated. His daughter, he would later recall, had been “the sunshine of [his] life.”

Grieving for his lost daughter, and stinging from the very public failure of his marriage, Ernie had no choice but to find a new wife—and, more importantly, a new grand duchess for Hesse-Darmstadt. He was the last of his family line, and if he didn’t produce an heir, the grand duchy would pass to Landgrave Friedrich Karl of Hesse. Not long after Elisabeth’s death, Ernie encountered the woman who would become his second wife: Princess Eleonore of Solms-Hohensolms-Lich. Ernie and Onor were much better suited for marriage than he and Victoria Melita had been, and the news of their betrothal was greeted with cheers both in Darmstadt and in the royal courts where his relatives resided. The couple married in Darmstadt in February 1905, with Onor wearing the same lace wedding gown that had been worn by Ernie’s mother, Princess Alice, decades earlier.

Gorgeous color photos of the front and back of the tiara are available in Geoffrey Munn’s Tiaras: A History of Splendour (2002), on page 285

Ernie presented the new jewel to Onor on Christmas Eve in 1905. The tiara remained a beloved part of Onor’s personal jewelry collection for the rest of her life. She posed in the tiara for a portrait by one of Ernie’s favorite artists, Hanns Pellar, when Pellar joined the artists’ colony in Darmstadt in 1911. Though she often chose to wear pieces from the grand ducal collection, including the large medieval-inspired tiara, for official photographs, the choice of the turquoise and moonstone tiara for this portrait feels like a very sentimental decision. Rather than an image that reflected her status as grand duchess, this artistic portrait, done by one of Ernie’s friends in a style that Ernie loved, feels like a much more personal depiction of Onor as a wife and mother.

Ernie, Onor, Georg Donatus, and Ludwig, ca. 1912

When Ernie passed away in October 1937, the world had changed remarkably. Ernie and Onor’s titles had been abolished in 1918 after World War I, and both of his sisters in Russia were killed. But Ernie had been so popular with the people of Darmstadt that he was able to stay in his home even after the war, retaining the palace as well as two of his hunting lodges. There, he and Onor raised both of their sons, Georg Donatus and Ludwig, who was born in 1908. When Ernie died, Hereditary Grand Duke Georg Donatus became the head of the family. Onor passed along the grand ducal jewels to his wife, Princess Cecilie of Greece and Denmark. Cecilie was photographed in several important pieces of grand ducal jewelry, posing for the kinds of portraits that Onor had sat for after becoming grand duchess. But no bejeweled images could change political reality: the couple would never sit on the grand ducal throne, which was just as well, as they were both members of the Nazi Party.

The turquoise and moonstone tiara, though, wasn’t passed on to Cecilie, as it was one of Onor’s personal possessions. Shortly after Ernie’s death, their second son, Ludwig, was scheduled to marry his British fiancee, Margaret “Peg” Geddes, in November in London. Onor decided to give the turquoise and moonstone tiara to her new daughter-in-law as a wedding present. She packed it in its box and placed it with the rest of her luggage, which was loaded on to an airplane that would take her, along with Georg Donatus, Cecilie, and their two older children, to England. Unfortunately, the plane went down in heavy fog in Belgium, killing everyone on board, including Onor.

The tiara, though, packed tightly in its box, managed to survive the fiery crash. Prince Ludwig’s wedding was held the day after the accident, even more somberly than had originally been planned. Some weeks afterward, the new Princess Peg was given the tiara as her wedding gift, fulfilling Onor’s wish for the piece. Peg wore it at sparkling occasions for the rest of her life. She and Ludwig had no children of their own, so after Peg’s death in 1997, the tiara was inherited by her nephew, the 3rd Baron Geddes, who is the deputy speaker of the House of Lords. You’ll sometimes spot the tiara on his wife, Susan, at events like the State Opening of Parliament.