In the ancient Roman world, official documents, such as army discharges, marriage contracts, property transfers, citizenship, etc. were often written on "double documents." These documents could be written on parchment, papyrus, or metal. Obviously, most surviving exempla are the metal type.
Now, on these documents, a text was written twice, in different sections. One of the sections was covered, sealed, and witnessed. The other section was left exposed for reference and use. If the authenticity of the exposed text was questioned, the sealed section could be opened and checked for discrepancies.
BYU, FARMerS, etc. have (anecdotally, to me) expressed interest that this is a corroborative proof of Book of Mormon authenticity, since it indicates that records and legal procedures in "the ancient world" were kept on metal plates that had "sealed" sections. In the Lee liberry, you can see a nice example from the reign of Trajan (98-117 CE) and their supposed significance for Latter-day Saints:
http://romanplates.byu.edu/about/what_significance.html
Despite the liberry's claim that "this pattern of documentary preservation, implemented in various media, was widely recognized in several ancient Near Eastern and Mediterranean civilizations," they all date from the ROMAN period, hundreds of years after Lehi et al. are supposed to have left the Near East forever. There are double documents from Israel that were discovered in the 1940s and 1950s, but these all date from the Bar Kokhba revolt in the 130s CE. If you know of earlier (say, 600 BCE) double documents from Semitic cultures and can direct me to their publications, I'll gladly revisit the issue.
This kind of cherry-picking of evidence to try to prove historicity in the BoM galls me to no end. It's disingenuous at worst, ignorant at best and an embarrassment to the BYU.
It also supports my contention that whoever wrote the BoM had a strong grounding in Classical literature and civilization.