My SILs first engagement she was given a family heirloom ring. It was her fiance's grandmother's ring. The agreement was that if they didn't get married and it was because of his infidelity that she could keep the ring, any other reason and she would have to give it back. They broke up (different religious beliefs that just didn't mesh) and she returned the ring.
My MIL told me she had some heirloom jewelry that she would give me but if we got divorced she wanted it back. This was about a week after we were married. :glare: She never gave me any jewelry and at that point I wouldn't have accepted it anyway.