Mithral Breatplate Armor question

[jyster]

So mithral breastplate armor takes away -3 of the -4 of the armor check penalty. It also says mithral is considered master worked, so is the -1 armor check penalty that MW takes away already included in the -3?

The same concerning Adamantine armor.

[knightofstyx]

jyster wrote:

So mithral breastplate armor takes away -3 of the -4 of the armor check penalty. It also says mithral is considered master worked, so is the -1 armor check penalty that MW takes away already included in the -3?

The same concerning Adamantine armor.

Yes, it's already included.

[Charender]

Seconded. If you look at the entry under special magic armor for elven chainmail, you will see that the armor check penalty is 3 less than normal chainmail.