"Irving Penn, Platinum Prints" was published in 2005. 191 pages. Plate number 10 is entitled "Jean Cocteau, 1948." According to the "Checklist of the Exhibition", pp. 171-6, plate 10 is a "platinum/palladium print on Bienfang mounted on aluminum, 1986." The text of the book states that Penn used muliple coats of platinum/palladium to make one image and that he often mounted the paper to the aluminum support before coating. He varied the mixture of pt to pl for each image.
Hope that helps,
Allen