Epic dungeon loot? I think so. But how do we know you didn't put that stuff there?
Easy way to know.
1 : Dungeons don't spawn diamond armour in them.
2 : They never have more than a certain amount of a thing per stack, you would never find a stack of 27 Golden Apples in one.
3 : Even IF they did spawn diamond armour, it would never be damaged.
4 : Dungeon chests tend to have everything placed rather randomly throughout the chest, it's hardly ever clomped in one area like it is in this screen shot.
I could go on if you really want, but that would be pointing out more things that are obvious.