Er... first, we're back to thinking about this FFP stuff after various other things have had increased priority with the little grey cells. But the new concept and thought that needs documenting is this:
There is a relationship between the amout of damage an attack does to the Victim and the Victim's Armour, dependant on the weapon used.
Take for example:
A hammer thunking down on:
Chain armour. Ow. Damage to the wearer. But the armour reforms to take the strike. [Damage to armour < Damage to wearer]
Plate armour. Oooh. Pain to the wearer. Also requiring a modicum of panel beating for the armour. [Damage to armour = Damage to wearer]
A crash helmet. Loud. Helmet smashed to heck. Owner unscathed, yet annoyed at losing an expensive bit of kit. [Damage to armour > Damage to wearer]
A manhole cover (laughez-vous pas, it was done in A Fistful of Dollars). Loud. But no damage to the strikee, and tbh, no damage to the manhole cover. [Damage to armour = Damage to wearer = 0]
So, this is a different (some would say more sophisticated) slant on the traditional - "bludgeoning, piercing, slashing" classification of weapons. The armour that is being attacked can take more, less or the same amount of damage than the wearer - or even be impervious.
yapman prolly had a more sophisticated idea of how the concept was meant to be expressed. But he can expound on it later :-)