The chest apparently only appears on your map after you have completed the game, (you probably just got close enough for it to be "found" when summoning the turkey) but I climbed down and got it before that point.
It contains all the special iron needed to craft the special items (well all the special iron needed that you don't get from completing missions.) and a couple of recipe's.
[spoiler=uniquecode]This is how you spoilers![/spoiler]
Last edited by SpinelesS; 11-20-2012 at 04:25 AM.