Box for storing jewelry or other small items. Pattern in the lid gives a very nice see-through effect when backlit.
An optional ring insert can be printed to give a very good overview of your fingerwear of all sizes.
Other things that will fit (without scaling the model up): A deck of cards, memory cards, coins, membership cards, rusty nails, earplugs, breath mints, batteries, a miniature giant space hamster, post-it notes, paperclips, matches and those small wooden pencils you get at IKEA.
The bottom will benefit by having a higher infill than the top to increase the weight and risk of tilting when open. Still, 30% is plenty.
25% infill should be enough.
Needs to be printed in TPE, NinjaFlex or other flexible/elastic material. This should be printed upside-down, and is designed to be printed without supports.
Lower infill can be an advantage for more flexibility. I used 20% with TPE filament, but could probably have gone down to 10%.
Make sure that the bottom 3-4 layers where the "tongues" are located are solid in order for them to stick to the model properly.
The hinge is designed to use a 1.75 mm filament as center (for 3 mm filament, scale the model to 171%). Heat and slightly flatten the ends of the filament using a soldering iron, wood burning pen or even a flat screwdriver heated with a lighter. As an example on how the filament center should look when done, see the second photo in another box I made here: http://www.thingiverse.com/make:179606
Aside from filament, you can use a thick steel wire, a piece a metal coat hanger or an 1.8 mm bicycle spoke as hinge center. Drill the holes up if needed, or simply scale the model up when printing.