The model that this is remixed from, as well as the original parametric model that that was generated from, has a provision for a gasket that can be printed in a flexible material and installed to help with weatherproofing and to protect against spills and other moisture ingress. The model (Commander Deck box) didn't include the gasket though, so I created one to be installed into it.
Print in a flexible filament such as TPU or TPE and then press into the channel in the lower half of the box. There should be a slight - but not overpowering - amount of springiness when closing the lid now.
The author remixed this model.
The model that this is remixed from has a provision built in for installation of a gasket to help with weatherproofing the contents of the box. However, the uploader did not create/include it, so I went and created the gasket so that the cards can be better protected against accidental spills and such.