In the 1930s and ’40s, an employee of the Massachusetts Archives stole a trove of original papers by the likes of George Washington, Benjamin Franklin and Paul Revere. Most of the documents were eventually recovered. But one paper, a 1780 letter from Alexander Hamilton to the Marquis de Lafayette, remained missing for decades—until it surfaced recently in Virginia.

Mark Pratt of the Associated Press reports that the precious document came to light last November, when a family from South Carolina tried to sell it to an auction house in Alexandria, Virginia; the letter had reportedly been in the possession of a relative who had died. A researcher at the auction house realized that something was amiss after consulting Founders Online, a website of the National Archives and Records Administration, which listed the letter as missing, according to the New York Times' Elisha Brown. The FBI was subsequently alerted to the document’s suspicious provenance.

A prosecutor for the U.S. Attorney’s Office in Massachusetts has now filed a complaint in federal court in Boston, asking that the Hamilton letter be returned to the government. It has been valued between $25,000 and $35,000.

Authorities believe that after it was stolen from the Massachusetts Archives, the letter ended up in the possession of a rare books and documents dealer in Syracuse, New York, who sold it to a member of the South Carolina family who tried to put it up for auction. The other documents swiped by the former archives employee, who was arrested in 1950, were also sold to dealers across the United States; according to CNN’s Amir Vera, the papers’ index reference numbers were removed or razored off.

Hamilton wrote the letter in the midst of the Revolutionary War, when he was a valued military officer among George Washington’s staff. The Founding Father’s brief missive was a warning to the Marquis de Lafayette, a French aristocrat and another close Washington associate, who came to the United States in 1777 to aid in the country’s fight against the British.

“We have just received advice from New York through different channels that the enemy are making an embarkation with which they menace the French fleet and army,” Hamilton cautions. “Fifty transports are said to have gone up the Sound to take in troops and proceed directly to Rhode Island.”

Hamilton and Lafayette were close friends; Hamilton was proficient in French, and he helped translate for the Marquis. Lafayette, in fact, once called Hamilton “my beloved friend in whose brotherly affection I felt equally proud and happy.”

The newly recovered letter suggests that Hamilton returned the sentiment. “I am My Dear Marquis,” he signs off, “with the truest affection, Yr. Most Obedt, A. Hamilton, Aide De Camp.”