Archival research doesn’t get much more exciting than the 2004 heist movie “National Treasure.” Nicolas Cage, playing a historian named Benjamin Franklin Gates, discovers a coded map on the back of the Declaration of Independence. Globe-spanning intrigue ensues — accompanied, offscreen, by a tsunami of eye-rolling by actual historians.

But now, in a bit of real-life archival drama, a pair of scholars are announcing a surprising discovery: a previously unknown early handwritten parchment of the Declaration, buried in a provincial archive in Britain.

The document is the only other 18th-century handwritten parchment Declaration known to exist besides the one from 1776 now displayed at the National Archives in Washington. It isn’t an official government document, like the 1776 parchment, but a display copy created in the mid-1780s, the researchers argue, by someone who wanted to influence debate over the Constitution.

It may not hold the key to a Masonic conspiracy, as in “National Treasure.” But its subtle details, the scholars argue, illuminate an enduring puzzle at the heart of American politics: Was the country founded by a unitary national people, or by a collection of states?