Answer:
Yes. There has been constructive delivery of the hat pin.
Step-by-step explanation:
In a situation that the key has been handed over to Laura by her grandmother Hannah, there has been a completed gift here because constructively, the hat pin has been delivered to Laura. This is so because, the vault has only one key, which means no other person is in possession of the key, and the hat pin is located inside the vault which only Laura now is purview to open it, for the reason that the key has been given to her. Hence, the gift is completed.