A rehash of https://www.thingiverse.com/thing:3736714 (by rh99) to have space for RFID coil and chip from inside of my workplaces entry fobs.
The spacers exist as some RFID coils are thicker than others.
Obviously you can simply glue the two shield halves together for a keyring.
Scale up 320% seems ideal.
It is not perfect due to my barely existent Blender skills
Edit: Uploaded updated files as friend had issue with the print, also split the spacer and the shield into seperate stl. print 2x shields and if required a spacer
White (though may redo in metallic red to save some painting)
Used Simplify 3D as Slicer
Personally I sanded with fine sandpaper, Glued together required parts with RFID inside, and painted with acrylics