A rare edition of the Magna Carta has been unearthed in a city library and is believed to be worth a staggering $21.3 million.

An archivist stumbled upon the document, a third of which is missing, at the Kent History and Library Centre.

The document was found in a Victorian scrapbook after archivist Dr. Mark Bateson was asked to search for another charter from the town of Sandwich.

The edition is believed to be one of only 24 copies across the world, and even with a third missing, is estimated to be worth millions.

The Magna Carta, between King John and rebel barons, dates back to 1215 and outlines basic rights with the principle that no one was above the law, including the king.

It is considered by many to be the beginning of democracy as well as the foundation for the Universal Declaration of Human Rights.

The latest copy is believed to date back to 1300 and, according to medieval history specialist Professor Nicolas Vincent from the University of East Anglia, could indicate that further copies exist.

“It must have been much more widely distributed than previously thought because if Sandwich had one … the chances are it went out to a lot of other towns,” Vincent said.

The 1300 Magna Carta was issued by Edward I and is believed to be the last one to be drawn up, the BBC reported.