I am interested in the question, what forms of evidence do contemporary Orthodox batei din accept to establish that someone is Jewish? In particular, if you, your parents and grand-parents are non-Orthodox, what sort of evidence would be acceptable to prove you are Jewish to Orthodox standards? As an example, I have recently learned that a non-Orthodox ketubah is sometimes (often?) not acceptable.
Here is an example of a list of required documentation required by an Orthodox Shul in South Africa (in South Africa all marriages that take place in Orthodox Shuls are authorized by the central Beth Din):
The purpose of this paperwork is to establish several facts that are vital in permitting an Orthodox wedding - including: a) that the bride and groom are Jewish b) that the bride and groom do not have the Halachic status of "Mamzer" c) that any previous marriages were terminated according to Halacha (death of spouse, or Halachic Get) d) if the groom is a Cohen there will be additional restrictions.
In light of this, it is hardly surprising that only documentation from recognized Orthodox shuls will be accepted to prove the above. Non-Orthodox groups do not follow Orthodox Halachic procedure with regard to conversions/divorces and documents from such groups simply do not prove that the prerequisites for an Orthodox marriage are met.