It's a particularly beautiful piece, I think. Certainly not easy to be worn as a tiara nowadays because it's rather short and high and clearly designed for another type of hairstyle than fashionable today, but it would nevertheless benefit if it was seperated from the necklace when being worn as a tiara. Judging from the photo below this is probably very easy to do, the mechanism seems to be some sort of latches on both sides of the tiara part.
It was just perfection as a necklace on Crown Princess Mette-Marit in her younger years.
But she also wore it very convincingly as a tiara (or a rather substantial hair comb) for King Harald's birthday celebrations in 2017.