Richard Suydam Palmer was the same age as Whistler. He may have been the son of Courtland Palmer, Sr (1800-1874).
He may have commissioned work from Whistler, in particular Copy after Ingres's 'Roger délivrant Angélique' y011.
Young, Andrew McLaren, Margaret F. MacDonald, Robin Spencer, and Hamish Miles, The Paintings of James McNeill Whistler, New Haven and London, 1980 ; The Correspondence of James McNeill Whistler, 1855-1903, edited by Margaret F. MacDonald, Patricia de Montfort and Nigel Thorp; including The Correspondence of Anna McNeill Whistler, 1855-1880, edited by Georgia Toutziari. On-line edition, University of Glasgow. http://www.whistler.arts.gla.ac.uk/correspondence.