A faded “copy” of the royal Magna Carta manuscript that Harvard University paid just $27.50 for is actually an ultra-rare original from the 14th century — likely worth nearly a million times that price, according to experts.

The groundbreaking document — which set limits on the King of England’s power and established the right to a fair trial — is one of seven copies of a 13th century version issued by King Edward I, according to academics who made the stunning discovery.

“Harvard had been sitting on it for all these years without realizing what it was,”said David Carpenter, a professor of medieval history at King’s College London.

“My reaction was one of amazement and, in a way, awe,” he said, adding the school had unknowingly owned the landmark papers for 80 years.

The exact value of the weather-worn charter wasn’t immediately clear  —  but a similar version from 1297 sold for $21.3 million at a Sotheby’s auction in New York in 2007.

The original Magna Carta, written in 1215, declared that kings must be subject to law and that residents are entitled to freedom from arbitrary imprisonment, along with other trailblazing foundations of modern American society.

There are four from 1215, and it was previously believed that only six of the 13th century versions existed — until Carpenter’s discovery.

Carpenter was searching the Harvard Law School Library website in December 2023 when he found the digitized document, which the school bought from a book dealer in 1946.

“I’d found one of the most rare documents and most significant documents in world constitutional history,” he said.

Carpenter teamed up with Nicholas Vincent, a professor of medieval history at the  University of East Anglia in England, to confirm the authenticity of the document.

First, he compared the charter to the other six originals from around 1300 and found the dimensions matched up. 

Vincent then looked at it with ultraviolet light and spectral imaging to examine small details not visible to the human eye.

The technology allowed the experts to compare the text word-for-word along with handwriting — including tiny important details such as a large capital ‘E’ in the word ‘Edwardus’ and elongated letters in the first line.

Harvard ultimately had to meet a high bar to prove its authenticity and did so “with flying colors,” Carpenter said.

The 13th century version of Magna Carta is “different from the previous versions in a whole series of small ways and the changes are found in every single one,” Carpenter said.

Harvard’s tattered copy of the Magna Carta is worth millions of dollars, Carpenter estimated — but the school has no plans to sell it.

School officials say owning it is a chance to inspire a new generation to learn about the Magna Carta, which played an important role in founding the US —  including with the Declaration of Independence and the Bill of Rights.

“We think of law libraries as places where people can come and understand the underpinnings of democracy,” said Amanda Watson, the assistant dean for library and information services at Harvard Law School. 

“To think that Magna Carta could inspire new generations of people to think about individual liberty and what that means and what self-governance means is very exciting,” she said.