American coin mechanisms in vending machines and arcade games have magnets to filter out Canadian quarters.
A coin drops at a known speed and the right coin will get pulled by the right amount by a magnet or get rejected.
If you have a silver coin or a small piece of copper pipe and a large, strong neodymium magnet, then you can easily observe this effect at home by putting the metal sample on a table and quickly waving the magnet past it as close as you can without touching it. The metal will slide across the table following the magnet, despite the metal itself not being magnetic, because the moving magnet induces eddy currents which temporarily create a magnetic field like an electromagnet. Other metals besides silver and copper exhibit weaker responses due to higher electrical resistivity.
TD Bank in Canada had coin counting machines for customers for a while. I dumped a few hundred $ in and was very happy when it kicked back some silver coins to me.
How nice of them!