Max J. Friedländer in The Michael Friedsam Collection. [completed 1928], p. 141, ascribes it to a Netherlandish Master, about 1520, and calls it "Portrait of Charles V, Holding the Sword and the Globe of the Empire"; notes that according to documents, the youthful prince was painted about 1520 after his coronation as emperor, most notably by Bernaert van Orley; suggests that this panel can be traced back to a Van Orley prototype.
Harry B. Wehle and Margaretta Salinger. The Metropolitan Museum of Art: A Catalogue of Early Flemish, Dutch and German Paintings. New York, 1947, p. 147, ill., believe this portrait dates after 1520, due to the imperial attributes of the sword and globe; assign the numerous surviving portraits of Charles V at the time of his 1520 Coronation to Van Orley's workshop; note that although our painting depends on the Van Orley prototype, "its style shows little relation to his".
Erik Larsen. Les primitifs flamands au Musée Metropolitain de New York. Utrecht, 1960, p. 96.
From Van Eyck to Bruegel: Early Netherlandish Painting in The Metropolitan Museum of Art. Ed. Maryan W. Ainsworth and Keith Christiansen. Exh. cat., The Metropolitan Museum of Art. New York, 1998, p. 409, ill.