~Cerobi Steppe~
*Chest 1: This one is found in the Northsward and has a 50% chance to appear. It should be in the west part of that area. Equip the Diamond Armlet and try the chests to the west. It only has a 10% chance to appear in one of those chests with the armlet on.

*Chest 2: This chest should be in the middle of the Crossfield area of Cerobi Steppe. Just like the first chest, the chest has a 50% chance to appear and the gun has a 10% chance of showing up with the DA equipped.

~Henne Mines~
This chest does not reappear. It's in a dead end in the Special Charter Shaft...i don't know which one. Just make sure to equip the Diamond armlet when you get to a chest if you really want to chance going through that part of the mines.

~Lhusu Mines~
Save at the Orange crystal, then go to site 9. There are two dead ends, you want the one more to the south. The chest has a 60% spawn rate. Do NOT equip the diamond armlet if you find it there, as you will not get it. There's a 50% chance of getting a Knot of Rust and a 50% chance of getting Fomalhaut. If you don't get it, you can reset, but i think the chest might respawn. It's probably best not to take that chance though. I didn't have to worry about it because i got it on my first try...i think my friend did too.

~Pharos-Subterra~
You will find this chest in Umbra. It has a 55% spawn rate in the southeast corner of the area. Just like Lhusu Mines, do NOT equip the DA. It has a 50% of holding the gun without the armlet equipped.