The Named
Plate is the tier you are given, or the tier you make, or the tier that is already dead and you are wearing it. It is the armor of the man who has decided the argument is over before it has started — the body is the wall, the wall is the iron, and the iron is the one who is still standing.
The only plate that moves is dwarven — the anvil-singers' masterwork, and it does not come off the anvil cheap. The dwarves make plate that moves the way the Vantari make bows that fly true at a gallop: the maker's name is on it, and the name is the promise, and the promise is the thing that moves. A masterwork plate is a story event, and the story is the one where the wall is the iron, and the iron is the one who is still standing, and the one who is standing is the one who is named.
In the Hand
The plate is the armor tier where the AGI cost is the whole argument: −40, and the fighter who wears it is the fighter who has decided the argument is not about being fast. It is the answer to everything — the flail, the long sword, the warhammer, the arrow — and the question it asks is the one the world has never learned to answer: what if the body is the wall, and the wall is the one who is still standing, and the one who is still standing is the one who is named?
"Plate is not armor. Plate is a name — and the name is the one on the anvil." — anvil-singer, Anvil-Singer Dwarf