Its nonextant original was written on vellum.    From Wordnet, Princeton University. 

Adjective : There are only three extant copies of the document.    From Dictionary.com. 

Reconstructing the nonextant plate text, like recovering manuscript or fair copy, aims at capturing the historical moment of first creation, but it resulted in abstractions of the kind Bob referred to as the "work" level, because the excavations cannot be verified and the methods deducing them are suspect.    From Wordnik.com.  [Introduction] Reference