I might suggest that if the dark stuff on the top of the LCII box is mold, just trash the box. Now.

Some might try to clean it but imo if you have moldy paper stuff, get it gone. 99% of the time it is not worth keeping and is doing more harm than good. And sometimes people do not know what they are doing and just spread spores around their house. A super-rare book might be worth it, but not an LCII box.