A manuscript long believed to be a copy of the Magna Carta, a landmark document in the rule of law and human rights, is in fact a rare original issued by King Edward I in 1300, according to Harvard Law School, which owns the manuscript.

The parchment was bought by Harvard in 1946 for $27.50, after being sold a year earlier at a London auction for £42, which was about $52 at the time, said a Harvard statement issued Thursday.

The document, measuring some 1.6 by 1.55 feet (1/2 meter by .47 meters), is now recognized as one of only seven surviving originals from Edward I’s 1300 issue of the foundational charter.

Researchers from King’s College London and the University of East Anglia authenticated the manuscript after comparisons with known originals and advanced imaging confirmed its textual and physical consistency.

“This is a fantastic discovery,” said Professor David Carpenter of King’s College London, according to Harvard’s statement.

“Harvard’s Magna Carta deserves celebration … as an original of one of the most significant documents in world constitutional history,” the statement quoted the academic as saying.

The parchment was traced back to Appleby, Westmorland, and passed through the hands of World War I air vice-marshal Forster Maynard, who inherited it.

Harvard officials hailed the discovery as a reminder of the enduring importance of rule of law.