frame-helmet

from The Century Dictionary.

• noun A helmet in which there is a solid frame, consisting of a ring round the brows with two, three, or more half-arches meeting at the top, and a boss to which the half-arches are bolted, the spaces between the arches being filled with lighter metal in plates, which can easily be bent to the slight curve required. Helmets of this form are common among peoples who are not skilful in forging.