I read about seer stones many years ago when I was in my early teens and that made perfect sense to me. It's nothing that tests my faith or should test yours. In fact, I think it's marvelous that the Lord provides the means whereby his prophets can accomplish what he has asked them to do! Thanks to the Bretheren and to you for sharing more information on this topic.
As an LDS Scientist I have been following the availability of information on the Prophet's seer stones for many years. This is an excellent book on what is known about the history of his various seer stones, which is, I'm sorry to say, very little. I would only add that Mother Smith said that the two stones in the original Urim and Thummim in the silver bows were so far apart in the spectacles that the Prophet had trouble using it. She stated that he finally took one of the two stones out of the silver frame and used it as a seer stone. It might have been one he used to translate some of the Book of Mormon and perhaps carried with him until he had to give the plates and the translators back to the angel Moroni. The Authors' suggestion that Mosiah II had a separate pair of seer stones from the ones he received that descended from the Brother of Jared is, in my opinion, kind of weak. Good book. Well documented research on a topic about which very little was written at the time.