111% Marble Suit?

I can confirm this isn’t a bug. The ancient chests in the labyrinth area of the ruins are booby trapped. Opening them will cause a black shadow to fly out and your character to say a line about it being trapped.

These chests have random effects and one of these effects is increasing or decreasing item durability. I have a 101% gold pickaxe and a 120% football helmet. They are cool objects to have and I keep them for display.