Today's tiara shares the same story as the Cartier Pearl Drop Tiara: it was once owned by Princess Charlotte of Monaco, and has since been seen only on her granddaughter Princess Caroline (perhaps...continue on). Made by Cartier, this piece is comprised of diamonds on a gold and silver frame. It was said to be a gift from Charlotte's father, Prince Louis II.
(Sidebar: I usually see the resemblance between Charlotte Casiraghi and her mother, but man - can't you see it with her namesake great-grandmother too?)
It shares its fringe design with the multitudes of other fringe tiaras that were produced in the good old tiara heydays. Like many of its fringe cousins, it can also be worn as a necklace by removing it from its frame.
In fact, Caroline seems to only be interested in wearing it in that necklace state. I suppose you can't blame her: the sunray effect is really quite stunning. (Her exclusive use of the piece as a necklace does bring up a valid question - perhaps this is not a tiara in the first place, but a necklace that was once worn as a diadem. It also must be noted that they could be two separate pieces entirely; fringes are hard to tell apart, and photos from Charlotte's time make it hard to tell.)
The same questions of possession go here as, again, the Cartier Pearl Drop. But I hope we see it on Charlene, and not just because I hope we see all of these tiaras again.