I can see the desiccant being an issue if you don't service the box and
change it out. I wonder if they are depending on the heat from the box
to keep things dry inside.

I have a downconverters handy. [Learn by destruction stuff from ebay.
;-)] They just use a sealed case. Both have a black fuzzy thing inside,
purpose unknown. I don't think it is a desiccant.

Pelican and similar cases have check valves. I just curse and yank
really hard and the ammo cases open. It is is impressive on some of the
cans with good seals.

I can't believe what they get for ammo cases these days. You would think
with a decade of war we would be awash with cases. I was driving around
Palmdale, spotted an Army surplus store, and decided to check it out.
Small ammo boxes I got for $5 at the flea market were $30. I've bought
real transit cases for that kind of money.