The man in the iron mask (called Lestang) was Count Ercolo Antonio Matthioli, a senator of Mantua, and private agent of Ferdinand Charles, Duke of Mantua. He suffered imprisonment of twenty-four years for having deceived Louis XIV. in a secret treaty for the purchase of the fortress of Casale, the key of Italy. The agents of Spain and Austria bribed him by out-bidding the Grande Monarque. The secrecy observed by all parties was inviolate, because the infamy of the transaction would not bear daylight. (H. G. A. Ellis: True History of the Iron Mask.)
M. Loiseleur utterly denies that Matthioli (sometimes called Giacomo) was the real homme du masque de fer (See Temple Bar, May, 1872, pp. 182-184); but Marius Topin, in The Man in the Iron Mask, maintains it as an indubitable fact. There is an English translation of Topin's book by Vizetelli, published by Smith and Elder.
There are several others “identified” as the veritable Iron Mask, e.g. emdash
(1) Louis, Due de Vermandois, natural son of Louis XIV. by De la Vallière, who was imprisoned for life because he gave the Dauphin a box on the ears. (Mèmoires Secrets pour servir à l'Histoire de Perse. This cannot be, as the duke died in camp, 1683.
(2) A young foreign nobleman, chamberlain of Queen Anne, and real father of Louis XIV. (A Dutch story.)
(3) Due de Beaufort, King of the Markets. (
(4) An elder brother of Louis
XIV., some say by the Duke of Buckingham, others by Cardinal
(5) Abbé Soulavie asserts it was a twin brother of Louis XIV., Maréchal Richelieu. This tale forms the basis of Zschokke's German tragedy, and Fournier's drama.
(6) Some maintain that it was Fouquet, the disgraced Minister of Finance to Louis XIV.
(7) Some that it was the Arminian Patriarch, Avedik.
(8) Some that it was the Duke of Monmouth; but he was executed on Tower Hill in 1685.
(9) In the Western Morning News (Plymouth, October 21st, 1893) we are told that Le Commandant Bazeries has deciphered a letter in cipher written by Louvois, Minister of War, to Catinat (Lieutenant-General in command of the army at Piedmont), desiring him to arrest M. de Bulonde for raising the siege of Conti; and to send him to the citadel of Pignerol.
“He was to be allowed to walk on the ramparts wearing a mask.”
Whatever the real name of this mysterious prisoner, he was interred in 1703 under the name of Marchiali, aged about forty-five. And the name is so registered in St. Paul's register, Paris; witnessed by M. de Rosarge (mayor of the Bastile) and M. Reilh (surgeon).
“The mask was made of black velvet on steel springs.”
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894