This includes any coffer-bound Artifact Armor pieces that may not have been in your posession at any time.
Any coffer-bound pieces of armor still in your inventory after restarting Artifact Armor quests will be unavailble from the coffers if still in your inventory upon restarting the quests available at level 50; assuming you decided to throw out/upgrade said pieces after this point. It will register as if you already took that step.
