Leon Cornforth lists Reformed Egyptian, iron, steel, and silk as being anachronisms in the Book of Mormon.
Leon Cornforth, Meeting the Mormon Challenge With Love: The Book For Mormons (Nampa, Idaho: Leon Cornforth, 1996), 21-22
Problems Regarding the Mormon Sacred Books. In spite of Mormon claims that The Book of Mormon, along with other Mormon books, should be the test by which we judge the authenticity of the Bible, non-Mormon scholars have pointed out some serious problems regarding the claims made for the authenticity of The Book of Mormon as an inspired revelation from God.
Language. The first of these problems has to do with language .The Holy Bible was first written in the ordinary languages commonly in use in those areas and at that time—Hebrew and Aramaic for the Old Testament and Greek for the New Testament. These were known languages that were widely spoken by the average persons living in those areas at the time the Bible was first written. If God intended to inspire another sacred book, or books, for the spiritual benefit of the world, we could expect that he would do so in another equally well-known, ordinary language in widespread use at the time. Yet Mormons claim that the original language in which The Book of Mormon was written on golden plates was “Reformed Egyptian” (The Book of Mormon, 9:32). Reformed Egyptian is not a known language as The Book of Mormon itself makes plain: “The Lord knoweth the things which we have written, and also that none other people knoweth our language; therefore he hath prepared means for the interpretation thereof.”
The result is that The Book of Mormon, unlike the Holy Bible, was not written in any known language in common use. We have no other documents or inscriptions of any sort that confirm the existence of such a language as “Reformed Egyptian” or that can help us to understand it. All we have is an English translation and the testimony of a single individual, Joseph Smith, Jr., that it is a faithful translation of the “Reformed Egyptian” language—a language unknown from any other source whatsoever.
Archaeology. Archaeological discoveries in Bible lands have upheld the historical and geographical statements of the Holy Scriptures. Of course, not every such detail given in the Bible can be independently corroborated by archaeology, but those statements that can be tested by archaeological findings have been supported.
Mormon scholars have made the same claim for The Book of Mormon—stating that archaeological discoveries in the Western Hemisphere have substantiated historical and geographical details given in The Book of Mormon. Such a claim is open to serious doubt. For example, the anthropology department of the Smithsonian Institution, in Washington, D.C., has questioned no less than eight The Book of Mormon statements that can be compared known archaeological facts. These disputed claims include the statements that the early Americans (Indians) were Israelites, that they used iron, steel, and silk (see Ether 10:23, 24; Jarom 8) or that they could have written in “Reformed Egyptian.” In short, the archaeological evidence seems to disprove a number of details given in The Book of Mormon. In fact where is even one bona fide artifact from the western hemisphere that unquestionably supports the story given in The Book of Mormon?