It appears that the Urim and Thummim in King Mosiah’s possession traces back to his grandfather Mosiah, to when the Jaredite record on stone was brought for translation (Omni 1:20-21). The Urim and Thummim delivered to Joseph Smith for use in translating the Book of Mormon, however, was the same one the brother of Jared had (Ether 3:22-28; D&C 17:1).