Not sure if it’s functional or not. British Museum describes it as:
The gilt-silver buckle has a rectangular plate with a bird’s head terminal in profile, scrollwork decoration and green glass inlays. The loop is oval, the tongue is hollow and has an animal-head terminal.
I’ve learned to call something shaped like the piece on the left a penannular. (https://duckduckgo.com/?t=ffab&q=penannular+cloak+pin&iax=images&ia=images) And have used them to pin together the two sides of a cloak’s collar. I’m not sure how the piece on the right would be used.
The right bit is a tongue rest for the belt buckle with a stylized bird head.
So the bird’s beak is not a functional hook?
Not sure if it’s functional or not. British Museum describes it as: