The helmet bears traces of the armorer's mark, an M beneath a crescent, possibly that of the Flemish armorer Guillem Margot, who worked for the Hapsburg court and was active in Brussels from 1505 to 1520.
Marking: Marked with a Roman M beneath a crescent.
Blair, Claude. "The Emperor Maximilian's Gift armour to King Henry VIII and the Silvered and Engraved Armour at the Tower of London." Archaeologia, or, Miscellaneous Tracts Relating to Antiquity 99 (1965). p. 37, pl. XIV a, b.
Terjanian, Pierre. "The King and the Armourers of Flanders." Henry VIII: Arms and the Man, 1509–2009 (2009). pp. 156, 159.