PHILADELPHIA -- A dealer of rare historic documents is selling a letter from Martin Luther King Jr. to a Philadelphia police officer who was assigned to protect him, expressing gratitude for the officer's concerns and minimizing his own worries for his personal safety.

In the May 21, 1965, note to Sgt. James Adair, a white Philadelphia police officer on security detail for a Law Day visit on May 1 to the University of Pennsylvania, King conveyed his appreciation for "the time and effort which you spent in providing both protection and traffic accompaniment for myself and the members of my party."

"While I hardly feel this necessary most of the time," the civil rights leader wrote, "it is both comforting and humbling to know that there are persons who are so concerned about my welfare."

Less than three years later, on April 4, 1968, King was assassinated in Memphis.

The Raab Collection in Philadelphia has set the price at $10,500 for the one-page typewritten letter, which was passed down through the police sergeant's family until descendants who wish to remain anonymous decided to put it up for sale. The note is on letterhead stationery of the Southern Christian Leadership Conference, the civil rights organization led by King, and is signed by him at the bottom.

Raab Collection Vice President Nathan Raab said King was aware of the near-constant death threats but chose to put them out of his mind, recognizing that many were baseless, so he could continue with his work.

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