term:

Ancient

ancient adj

: existing from a long past date
;specif
: having had an uninterrupted existence of 20 to 30 or more years NOTE: Things and esp. documents that are ancient benefit from a presumption that they are valid even though proof of their validity may be unavailable due to lapse of memory, absence of witnesses, or loss of documents.

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.