Quick question on mithral armor

[Grog]

Spell failure chances for armors and shields made from mithral are decreased by 10%, maximum Dexterity bonus is increased by 2, and armor check penalties are lessened by 3 (to a minimum of 0).

(...)

Weapons or armors fashioned from mithral are always masterwork items as well; the masterwork cost is included in the prices given below.

Making armor out of mithral reduces the armor check penalty by 3. However, mithral armor is always considered masterwork, and masterwork armor reduces the armor check penalty by 1. My question is, does this stack (thereby making all mithral armor effectively reduce the armor check penalty by 4?) It's not any kind of named bonus, after all....

 

[IanB]

The masterwork bonus is already factored in. The entry for adamantine makes this a little more clear, since adamantine doesn't have an extra armor check reduction on top of that already provided by the masterwork quality.

 

[Krafen]

I read the line "Weapons or armors fashioned from mithral are always masterwork items as well; the masterwork cost is included in the prices given below." to mean the masterwork reduction in armor check penalty is in addition to the reduction due to the armor being made of mithral.