This piece is from the Stilla nation. It was found in the Old Crown tomb. It is a head dress intended only for burial. It was assembled from thin pieces of gold sheet. The ornaments suggest wings or feathers, although the actual purpose is not known.
Albus was put in Slytherin. The sorting didn't make a bad choice because maybe Albus could raise the Slytherin House liking considering everyone in the Harry Potter world be hating on them. So with a Potter in Slytherin it could help the house.