A 30mm x 4.5mm Firesteel accompanied by a 25mm x 13mm Saw.
Use the saw blade to strike the firesteel and create a small shower of sparks to light your tinder. Although bigger firesteels will obviously create a larger shower of sparks, this compact combination fits in the wallet for EDC or works well into a minimalist survival kit.
(Coin not included)
Tip : Cotton balls covered in petroleum jelly work as an ideal fire starter.