1) pick a 5 euro cents coin
2) using a stepped bit – easier – or a normal bit drill a hole in the center
3) pass a piece of cord trough the hole and make a node creating a loop – I used a bit of paracord (parachute cord) I had laying around that it is worth more than the coin 🙂
4) attach it anywhere you want: your keys, the Hasselblad strap, your backpack.
The important thing is that you will have this object with you if (when) a jamming should happen.
Hell, this thing is so cheap and easy to do that you can also make tens of them, and spread them everywhere!