Portrait of mary sylvester. Object Type: painting. Genre: portrait. Date: 1754. Place of creation: United States of America. Dimensions: 49 7/8 x 40 in. (126.7 x 101.6 cm). Medium: oil on canvas. Depicted People: Mary Dering. Collection: Metropolitan Museum of Art. Mary Sylvester (later Mrs Thomas Dering) 1754 by Joseph Blackburn