Researchers have discovered a unique copy of the U.S. Declaration of Independence in an unexpected place - England.

The copy, similar to the one viewed by millions each year at the National Archives in Washington has been locked away in a local records office in southeast England forgotten by historians.

Its significance wasn't understood until recently, when Harvard researcher Emily Sneff stumbled on a mention in a catalog of the office's holdings. Something tickled her curiosity: the copy was written on parchment, and thus unique.

Sneff's sleuthing, together with that of Harvard professor Danielle Allen, led to a discovery that could shed new light on the founding document of the United States.

Sneff said Monday: "I thought, 'Holy history, Batman! We'd seen a lot of copies, but nothing like this."