Hurgak

The Helmets made in Isengard by Saruman´s Orcs were unlike typical orcish armor.Still heavy and crude they looked more like mannish armor and was decorated with S-runes and the sign of the white hand.

speculations
Tolkien doesn´t describe the Armor of Isengard, but the close distance to Rohan may imply that it may have been influenced by the common Armor of the Riddermark, which in turn may be imagined similar to anglo-saxon or late goth armor.

Peter Jackson´s movie trilogy shows the Uruk-Hai Helmets as being similar to sallets.There were different types of Isengard Helmets in the movie trilogy:
 * a Scout model
 * a Pikesman´s model
 * a swordsman´s model
 * a Berserker model
 * a sapper and crossbowman´s model
 * a captain´s model