This is a typical example of a Norman helmet.

This bowl shape seems to have proved an effective defence against swords, axes and maces, since they remained popular in various part of Europe, especially the east, until the thirteenth century. The Saint Wenceslas helmet is a mysterious archeological find. The bowl of the helmet is being dated on 10th or 11th century, but the diadem (nasal and banding) seem to be earlier, from the late 8th or early 9th century. Some archeologists claim that the diadem was taken from a lost Carolingian helmet, because of its ornament. The iron skull is forged in one piece, with an iron nasal and bottom reinforcing rim riveted in place and decorated with silver overlay in the form of interlaced strapwork; the nasal is decorated in the same manner with a conventionalized crucifix motif. The helmet is preserved in the Cathedral Treasury in Prague, and it is said to have belonged to Saint Wenceslas, Duke of Bohemia. Duke of Czech Wenceslas was son of Vratislav. After gaining the throne at the age of eighteen, he promoted the spread of Christianity throughout Bohemia. This was accomplished not only by building churches, such as future St Vitus Cathedral in Prague, but also by his acquiescence to the influence of the Holy Roman Empire. However Czech nobles wanted to stay in pagan religion and to preserve independence of their country. Boleslaus, the younger brother of Wenceslas, has plotted conspiracy with nobles against Duke. In 935 (or 929) Wenceslas was murdered by being hacked to death on his way to church in Stara Boleslav town. That way Boleslaus succeeded after his brother and is known as Boleslaus I Ukrutný (Boleslaus the Cruel). Wenceslas was canonised as a saint due to his martyr's death and he is the patron of Czech Republic.

(In part based on : Arms and Armor of Medieval Knight by D. Edge and J. M. Paddock.)