Dr. Jim Huffman waffled whether to put down $900 for a painting he liked at a Lexington, Kentucky, antique store. The ophthalmologist finally bought it and then sent the work to an art restorer. A cleaning revealed the artist's signature: Robert Scott Duncanson, a noted 19th-century artist who was the first African-American painter to gain international recognition. Now valued at about $100,000, the work is on loan to the Speed Art Museum.