Isabella Gardner and John Singer Sargent first met in 1886 in the artist’s studio in London. There Gardner admired Sargent’s daring portrait Madame X (now the Metropolitan Museum of Art, New York) so much that she commissioned him to paint her likeness. This sketch of Gardner’s head set against a dark background was probably an early preparatory drawing for the oil portrait which Sargent painted from December 1887 to January 1888. Gardner inscribed the drawing with Sargent’s name and the date, most likely recording when she received the sympathetic portrait from him as a gift.
Source: Oliver Tostmann and Anne-Marie Eze, The Inscrutable Eye: Watercolors by John Singer Sargent in Isabella Stewart Gardner’s Collection, exhibition on view in the Museum's Fenway Gallery, October 31, 2013–January 20, 2014.