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Most of the grand tiaras worn by members of the British royal family have long, carefully-documented histories. But then some, like this delicate diamond and aquamarine tiara, are a bit more enigmatic.

With this mysterious sparkler, we’ve got at least some background to go on. The tiara was worn by Queen Elizabeth II on a visit to Canada in 1970. Many royal jewel experts thought that it had been one of the pieces broken up and used to form the queen’s larger Brazilian Aquamarine Tiara.

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In 2012, though, the Countess of Wessex unexpectedly appeared in the tiara at a dinner held the night before the wedding of Hereditary Grand Duke Guillaume of Luxembourg. She wore it again at the wedding of Princess Madeleine of Sweden in 2013 (pictured below).

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So the Brazilian Aquamarine theory appears to be false, because the Canadian tiara does not appear to have been altered from its 1970 form. Even the tiara’s frame appears to be identical. Is it a totally independent piece and not a part of the series of aquamarines the queen received from Brazil during the 1960s? Or were other stones used to flesh out the Brazilian Aquamarine Tiara, leaving this one in its original state? The plot thickens…