[Endoperez]

I'm at home now and can test this (I quoted Zen at school). Items that increase normal leadership by 100 or more result in Awe, regardless of what the particular unit started with.
Zen might have meant that with "magical leadership", as opposed to magic leadership, because his formula works.

For clarity's sake, I'll rewrite it here as so:
(item bonus to leadership - 75)/25

Result of 1 will be Awe +0 or +1 to existing Awe, 2 will be +1 or +2 to existing awe, etc.

Because most leadership-increasing items are weapons this will rarely come into play. I think only Twin Spears are meant to be both weapons and leadership-increasers. O'al Kan's Sceptre doesn't seem to be bad in melee, either (armor-negating, area stun, 50% resistance and Awe with another +50 leadership item).

This also explains why Crown of Overmight gives Awe, or rather why the Awe isn't listed in the manual.