I'm actually convinced that, beyond the fourth wall, it's a sort-of proto-Silmaril that Tolkien later meant to disown because he hadn't thought things through thoroughly enough at that point. In-world, the question remains wither it's a Silmaril or not, and while everything about the thing itself is in favour of it being a Silmaril, the Elves should be much more upset in general about the thing coming to light if it was. Thranduil would have recognised it; and Galadriel would have had to do something about it. By its material properties it is Maedhros' Silmaril (we even know it ended up in a fiery mountain far away), by the reaction to the thing, it can't be.

I'm looking forwards to seeing where Peter Jackson is going to go there.