It is assumed that an appropriate type of head armoring will be added to the suit of armor in order to allow uniform protection of the wearer. Wearing of a “great helm” adds the appropriate weight and restricts vision to the front 60″ only, but it gives the head AC 1. If a helmet is not worn, 1 blow in 6 will strike at the AC 10 head, unless the opponent is intelligent, in which case 1 blow in 2 will be aimed at the AC 10 head (d6, 1-3 = head blow).
Just read this part for first time. Anyone who hasn’t bought a helmet, I suggest you do so. I love yelling “HEADSHOT!”