EDIT : VERSION 2
You can find 2 more files, Case5deg.stl and Cover5deg.stl : I added a 5 degrees draft angle on the closing surfaces to have a better "clic" and the box cannot open herself.
I wanted a slim case for my Geekcreit® ATmega328P Nano V3 (a copy of the Arduino Nano board you can find on Banggood) and the model from Mean122 was nice, but only for original Arduino (components position differ slightly).
I also wanted a case for situations without pins access, but with an output cable directly soldered on the board : I did this one.
No components footprint to be compatible with all boards, a 3mm cable output, a window to see the LEDs and a reset button, simple and beautiful ;-)