{I sent in something on this before but I believe it got lost in the weekend accident the moderator described.  This is an improved version anyway so no loss the first time.  HL}  The standard work on detecting forgeries of ancient documents  is probably the writing of Friedrich Blass, "Hermeneutrik und  Kritik," _Einleitende und Hilfsdisziplinen_, vol 1 of _Handbuch der Klassischen Altertums- wissenshaft_ (Noerdlingen: Beck, 1886).  Portions of this are described in Nibley, _The  Prophetic Book op Mormon_, pp 219-242 (SLC:  Deseret Book, 1989). (If you want to attempt reading this be forewarned.  Nibley describes Blass as a typical German scholar who claims little knowledge of his subject, then proceeds to exhaust both the subject and the reader.)  Nibley's extract from Blass's work is in the form of "rules for forgers."  It makes interesting reading.  I confess that I have not read Blass's work, only Nibley's extract thereof.  My German falls far short of what would be required and as far as I know there is no English translation available.  However, I believe the techniques he describes are known widely enough that  any competent classical scholar could examine a purportedly ancient document and at least determine if it is consistent with what one  would expect of a genuine document of that time frame.  We will not  be able to prove who wrote it but at least we should be able to  determine with reasonable confidence if it is from that time and  culture or is a later forgery.  Actually there are 2 types of purportedly ancient documents:  1.  Alleged actual holographs or early copies thereof.  For example the Dead Sea Scrolls.  These can be tested by various scientific means to determine the age of the paper, inks, and objects found with them.  This can provide a pretty clear dating of the actual physical objects.  2.  Documents claiming to be copies of ancient works although the copy itself may be much more recent.  For example we might find a document which monks in a monastary claim is a copy of something from centuries ago (perhaps even having been through several generations of copists).  This is more of a problem but can still  be tested (although the test is not likely to be simple).  We cannot expect a test of the age of the physical objects to tell us much so we must confine our testing to the text itself.  It is important to remember that none of these tests can tell us if the document is really what it claims to be.  They can only date the document and identify its culture of origin.  For example I've heard of a letter supposed to have been written by Jesus himself to a king in what is now Iraq.  If this document were to actually turn up scholars could date the paper and ink (assuming they have the holograph).  They could check the language, content and writing style to see if they are consistent with what would be expected of a Palestinian Jew of that time.  However even if all test results were positive there is no way to determine if Jesus himself actually wrote it.  We would know what time and culture it came from but (barring a known sample of Jesus handwriting or other clues for  comparison) scholarship must stop there.  There is seldom any way to determine who the actual author was.  As I say, I'm no expert on Blas's work.  I do remember some of the tests which can be applied to alleged copies of ancient works.   Specifically we might ask:  1.  Is the document internally consistent?  Does it contradict itself?  If the work it is short it would be relatively easy to  maintain internal consistency, even if it is a forgery.  The  longer the forgery the more difficult it is to maintain consistency. For this reason most successful forgers stick to short documents.  2.  Is it consistent with the history and geography of the time? Again a short, non-specific work might not be testable but if the writing is of any significant length no latter-day forger would be able to escape detection.  Here we look for the minor, inconspicuous things which someone from that culture would get right without even thinking about it but which a later forger would find too numerous  and trivial to check.  The devil is in the details.  3.  What about the literary style of the work, figures of speech etc.  Any ancient writer would almost certainly speak in ways that  seem strange to us.  Are there any such odd phrases in this book?   If so do they fit in with the culture?  Of course there are complications if the document has been translated, or possibly even if somebody just updated language when he copied it.  A few cases of language not from the culture claimed may be allowed in recent copies.  They cause problems and reduce certainty to be sure but don't necessarily prove forgery.  These tests can be quite effective (given enough material to work  with) but they are not easy.  They require the skills of the  historian, the linguist, the anthropologist etc.  The questions to  ask are, "Is every aspect of this document consistent with what we  know about the culture of claimed origin?"  If there are things  which don't fit how significant are they?  Are problem areas due to our lack of knowledge, later changes by copists or are they really  significant?  There will often be some ambiguity since we never know everything about the culture.