I searched and saw your answer to this question, but it didn’t answer it. Do you or any church historians know what happened to the brass plates after Mormon transferred them onto the gold plates? I have found that he transferred the brass plates, small plates of Nephi and the Large plates of Nephi, but what happened to the originals once they were transferred? Thanks.
I’m afraid you’re mistaken about the brass plates. Mormon did not transfer them to the gold plates passed on to Joseph Smith. I’ve written before about the contents of the unsealed portion of the plates. I quote from it for consistency.
What Moroni hid up in the Hill Cumorah and delivered to Joseph Smith was one volume of gold plates containing three separate records. The first third of the set contained two records; these were 1) Mormon’s abridgment of the Large Plates of Nephi, Moroni’s abridgment of the plates of the Jaredites, Mormon’s and Moroni’s personal accounts, and 2) the entire original record called the Small Plates of Nephi. The first part of our Book of Mormon, from First Nephi through Omni is a translation of the Small Plates which were written primarily by Nephi and Jacob, with shortentries from the remaining leaders of the Nephites down to Omni, who lived somewhere between 279 and 130 B.C. The remaining two thirds of the record was sealed.
The passing of the Plates
While the small plates quote extensively the words of Isaiah from the brass plates, the brass plates themselves weren’t included as part of the abridgement. The brass plates were passed down with the Nephite records until came into the hands of Nephi the son of Nephi (3 Nephi 1:2). If Mormon is editorializing in 3 Nephi 10 (as opposed to the abridged author), then he very probably had the Jerusalem records and passed them on to his son (or at the very least, had records that referenced Jacob’s testimony). Regardless, the pattern for passing on sacred and secular records is mentioned throughout The Book of Mormon, so it is quite likely that Mormon preserved the brass plates with the other Nephite records when he placed them in Cumorah (Mormon 6:6).
Preservation of the Plates
These records have been preserved and are in the care of Moroni today (in accordance with dispensational authority). President Brigham Young related Oliver Cowdery’s vision of these records:
“When Joseph got the plates, the angel instructed him to carry them back to the hill Cumorah, which he did. Oliver says that when Joseph and Oliver went there, the hill opened, and they walked into a cave, in which there was a large and spacious room. He says he did not think, at the time, whether they had the light of the sun or artificial light; but that it was just as light as day. They laid the plates on a table; it was a large table that stood in the room. Under this table there was a pile of plates as much as two feet high, and there were altogether in this room more plates than probably many wagon loads; they were piled up in the corners and along the walls. The first time they went there the sword of Laban hung upon the wall; but when they went again it had been taken down and laid upon the table across the gold plates; it was unsheathed, and on it was written these words: ‘This sword will never be sheathed again until the kingdoms of this world become the kingdom of our God and his Christ.'” (Journal of Discourses volume 19, page 38).