I've designed this Geocache box with the idea of being magnetic.
It can hold up to 4 magnets on little holes at the bottom.
The first version was in PLA and stayed outside for a year but lost the magnets and now is missing so I recommend using PETG for this, will hold better under the rain and hot/cold weather.
Doesn't Matter
Yes
0.2 it's ok
Generic PETG
PETG