This is a key fob for the RFID tag from a Tesla Key Card.  Suitable for attaching to a key chain. 

1. Use acetone in a glass jar to extract the electronics from a Tesla Key Card. It takes 45 minutes to extract the electronics from the Key Card.  Be sure to use a glass jar. 
2. Test that the electronics do indeed open your car and weren't damaged during the acetone process.
3. Print the three parts from the 3MF file (or see ProjectA.scad for instructions for remixing.  The three individual STL files are also included separately).  I used PLA and it seemed strong enough.
4. Place the RFID chip inside of the rectangular compartment, route the two wires through the two slots. 
5. Put the rectangular cover over the rectangular compartment.
6. Form the RFID rectangular copper wire loop into a multi-wrap round loop inside the cavity:  cross-over to turn the rectangular loop in an 8, then fold-over to make a circle. Do a couple times so that the loop is the same size as the round compartment.
7. Set the round cover into the round compartment.
8. Test that the electronics do indeed open your car.  This verifies that your copper loop is a sufficient antenna.
9. Hold the round cover on with clamps (clothes pins).  Then use superglue to glue the round cover along the seam.
10. Wait 10 minutes.
11. Move the clamps to different locations, glue the remaining locations.