Recently I was going back and searching for AF armor to upgrade. I did get the coffer keys and armor for these jobs. But I also ran into many Area chest. When I opened the area chest, they would reward me with meaningless items like lvl 30 rings or 50 necklaces.
My suggestion is for area treasure chest, upgrade those chest with pages 1 - 5. This would give incentive to open these while people locate coffers.