LONDON — British researchers have announced the discovery of a rare original copy of America’s Declaration of Independence — just in time for the Fourth of July.

Katrina McClintock, a spokeswoman at the National Archives, said today that a researcher accidentally discovered the “Dunlap print,” named after a printer, several months ago. The find was announced only after it could be properly catalogued.

Edward Hampshire, the National Archives’ specialist in colonial materials, said the find was “incredibly exciting.”

“It is likely that only around 200 of these were ever printed, so uncovering a new one nearly 250 years later is extremely rare, especially one in such good condition,” he said.

He said the declaration is one of the most important documents in history because it marks the birth of the United States.

The last Dunlap print to be found was sold at an auction for $8.14 million in 2000.

National Archives officials said they weren’t sure how the Declaration of Independence copy ended up there.

Archives spokeswoman Frances McDarby said it was “possible that an American coastal vessel was intercepted by the British navy and that is how the document was able to come into our possession.”

The prints, known collectively as the Dunlap Broadside, were the first copies of the Declaration of Independence. They were printed by John Dunlap of Philadelphia and distributed to political and military leaders, including George Washington, and dispatched throughout the colonies to be read to the public.