Martin Thomas Lamb writes that the gold plates, or any metal plates referenced in the Book of Mormon, never existed in antiquity.
M. T. Lamb, The Golden Bible; or, the Book of Mormon: Is it from God? (New York: Ward & Drummond, 1887), 11
IS THIS BOOK INSPIRED OF GOD?
Every good honest Mormon says "Yes," and believes it fully. He believes that the Book of Mormon is a true historical record of God's dealings with his ancient people upon this continent; that its contents were "given by inspiration of God," and "confirmed by the ministering of angels;" that the men who composed its pages wrote as they were moved by the Holy Ghost; that Joseph Smith translated it "by the gift and power of God;" that it is, and was designed to be, a revelation of God's will to men, and a "guide in faith and practice."
But after a careful study of the book, a conscientious and painstaking examination of all the evidences he has been able to gather both for and against it, the author of these pages has been forced to reject every one of the above claims. He is compelled to believe that no such peoples as described in the Book of Mormon ever lived upon this contingent; that no such records were ever engraved upon golden plates, or any other plates, in the early ages; . . .