Only recently have we discovered steel swords in the Near East so it seems odd that Joseph Smith would have included this in the Book of Mormon.
Evidence Central explains:
Before archaeologists discovered the long steel sword in Jericho, the description of the sword of Laban in the Book of Mormon may have seemed too fantastic to be true. Some people laughed at the notion of a steel sword in Jerusalem in 600 BC. Similarly, the idea that an ancient Near Eastern sword could be long enough for Nephi to decapitate Laban in the manner described in the Book of Mormon also seemed unbelievable. And then, 150 years after the Book of Mormon was published, archaeologists discovered an artifact that showed that the Book of Mormon’s account was not so unbelievable after all.– Book of Mormon Central – What Was the Sword of Laban Like?
Why would Joseph take a chance on including steel swords in Jerusalem if they had not been discovered yet?