Note 17 — HISTORY OF THE IRON MASK.
Reading edition
Charles III., Duke of Mantua, father of Ferdinand Charles IV., the reigning Duke, had the command of the Imperial Army in Italy, and took upon himself the office of Vicar General of the Empire in Italy, during the interregnum which followed the death of the Emperor Ferdinand III. in 1657, in virtue of a diploma, lately granted to him by that Prince. His right was contested by the Duke of Savoy, who, upon the ground of old usage, claimed the office for himself. The Electors of the Empire annulled the appointment of the Duke of Mantua.