From my Samples, Singulars, and Somethings Completely Different collection -

Templar great helm sized for youth or small adult. 16 gauge mild steel, classic four panel and flat top construction, engraved Templar sigil on right cheek, Maltese cross patterned breath holes on the right.

height, front seam: 12 1/2"
height, side seam: 11"
outer circumference at mid seam: 27 1/2"
outer circumference at top seam: 21"
top plate: 6 1/2" front to back x 6" wide
bottom opening: 9 1/2" front to back and 8" wide
weight: 4 lb 6.5 oz