Okay, thank you. Further questions:
YS252:
"Optionally, instead of block strength, you can opt to have the effect work as Armor or as a zone border instead. If you choose the Armor effect, the armor rating is equal to half (rounded down) the shifts put into the spell. The advantage to doing this is that the Armor effect only ends when the spell duration ends—the armor survives a bypassing attack."
How does this translate into an item. I can read Harry's coat and it's Armor:2 for 3 uses or something like that. If I understand how that works that Armor rating expends a use for every attack levied against it, so it lacks this basic advantage above of lasting until the spell duration ends.
Is the advantage and choice here that Armor is reflexive and Block is anticipatory? Or another way, the Armor would be active if the wearer were hit with an Ambush attack, but the Block would not?
If I'm right, then why choose Armor for an item? Ever...
Say Harry's Duster is Block:4 or Armor:2, 3x per session. Only one roll can reduce the shifts from an attack, so if 4 is higher than any shield spell or dodge roll, he should use it as a block, otherwise, he should use the armor aspect instead. The reason it shifting is useful is to stack defenses. For example:
Harry uses his shield bracelet to throw up a Block:5 shield. He gets attacked by a Weapon:2 gun shot at +6. His Duster does nothing at Block:4, as it's worse than his shield, but his duster can give him Armor:2; reducing the 3 stress hit to 1 stress.