A month ago my brother gave me an old .50 cal ammo box. Great for storing my knives in a thought. And threw in some of the blades I seldom use, and put it away, allong with my sharpening tools.
Wen't to fetch a knife just now, and when I opened the lid, the smell of mould greeted me.
The entire interior of the container was covered in it. Including my little strop, and the leather sheats. Even the plastic mora sheaths had a dusting of mould on them. And my Mora 162 whitling knife was covered in rust.
It might not be the container itself, it may be something elese. But I have work ahead saving the sheats and fixing my blades...