Knobelsdorff’s 1735 portrait of the young Frederick the Great in armor attended by a Black African page who stands by the prince’s helmet opens a window into the long and complex association of dark skin [...] sometimes wore another kind of metal, the slave collar. Paul H. D. Kaplan is Professor of Art History at Purchase College, SUNY. He is the author of “The Rise of the Black Magus in Western Art” (1985) and [...] University Press’s “The Image of the Black in Western Art” (new ed., 2010-2012), and a more recent publication, “Contraband Guides: Race, Transatlantic Culture and the Arts in the Civil War Era” (Penn