Sotheby's will offer the previously unknown document Thursday along with two others: the scribbled notes for a speech King planned to deliver in Memphis, Tennessee, three days after he was assassinated, and a letter of condolence from President Lyndon B. Johnson to King's widow.
The documents are owned by singer-actor Harry Belafonte, a friend and host on King's visits to New York beginning in the mid-1950s.
The auction house put the overall pre-sale estimate for the three documents at $750,000 to $1.13 million, with the Vietnam speech valued at $500,000 to $800,000.
