Overview - Chests and Coffers in Final Fantasy XI are a way of obtaining items and gil by a method unlike any other in the game. The treasure from chests and coffers includes gil, general armor and weapons, precious stones, map key items, rewards or requirements of Artifact quests, and more. Every character will need to access chests or coffers while leveling up in FFXI; completing a full set of Artifact quests for a job requires opening at least three chests or coffers. For most jobs, this involves going into the Dungeon where the chest or coffer is located, and killing specific mobs until the appropriate treasure key is dropped for it. A Thief job of high enough character level does not need the specific chest or coffer key, and instead go straight to finding the chest or coffer. Once the chest or coffer is found, it is opened with the appropriate key; a Thief can attempt to pick it, by using special generic key items. An item or chunk of  FFXI Gil is obtained whenever a coffer or chest is opened. The coffer or chest then reloads in the zone after a period of time, and can be opened again. This guide explains the specifics of going through these steps, and provides a full list of the chest and coffer contents.

Differences Between Chests and Coffers - Coffers and chests are fairly similar in most aspects of how they work: they both take specific keys to open, a Thief can pick them, and each reloads regularly in their zone. There are some zones that only have chests, other zones where there are only coffers, and a handful of zones that contain both. Chests and coffers each have their own independent spawn locations and time; both a chest and a coffer can be loaded at once, in the zones where they both exist. Chests are located in many of the Dungeon zones, from mobs level 15 all the way up into the 60s. Coffers are found only in higher level zones; almost all mobs that drop coffer keys are level 60+. In zones that contain both chests and coffers, the mobs which drop chest keys are always lower level than the mobs that drop the coffer keys. Since they are harder to open, coffers tend to give more FFXI Gil and better items than chests. Thieves have a harder time picking coffers than chests, with potentially much more dangerous results if they fail.