If you want a safe and snug place to store and show off your marbles at the same time, I recommend these transparent marble show off trays.
When I get a new batch of marbles, I spread out several of these to use for the initial sorting. I also use them for long-term storage.
Each has 35 pockets to safely store 5/8" - 3/4" marbles, and each has a slide-on see-through cover to hold them in place snugly. You can squeeze 7/8" marbles in these too.
Besides being small and light, these trays are transparent which allows the light come in from all angles. Marbles look better in these trays and you can safely "rattle" them around, allowing the marbles to roll side-to-side for better viewing angles.
You can pick them up over at Land of Marbles. I wish they were cheaper, but if you buy in larger quantities the price drops.