(CNN) A second parchment copy of the Declaration of Independence has been found. In England, of all places.

It's a remarkable discovery, because the only other parchment manuscript copy of the historic document is housed behind glass at the National Archives in Washington, DC.

You see, most copies of the Declaration of Independence are just that -- copies. They are facsimiles of the one housed in the National Archives, which is called the Matlack Declaration and regarded as the official document.

An honor guard stands next to the original copies of the Declaration of Independence, the Constitution and the Bill of Rights July 4, 2001 at the National Archives in Washington, D. C.

Now comes this discovery.

Danielle Allen and Emily Sneff -- both researchers at Harvard University -- found this parchment manuscript in a records office in Sussex County, England. So they're calling it The Sussex Declaration.

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