A magic coin.
A Magic Coin is an object used by witches or demons for a variety of purposes.
Tracking Coin[]
It acts as both a tracking device and a listening device. The coin's magic is strong enough that not even hex bags can defeat its power. Crowley planted one of these coins in the Winchesters' Impala after their first encounter. He used this device to spy on the Winchesters and learn about their plot to collect the four Rings of the Horsemen to re-open the Cage and re-imprison Lucifer. Later, another demon planted a magic coin on Crowley, allowing a hellhound to track him.
Romanian Coin[]
Maggie Stark's altar with her hex coins.
A Romanian Cyrillic coin from the 15th to the 19th century which can help focus the power of a hex. Maggie Stark was angry at Don Stark for having an affair and started to kill people associated with him by placing a magical coin near them and working in an incantation:
"Puterea magiei negre te condamnă la suferință și moarte"
(Romanian for: "The power of black magic is sentencing you to suffering and death.")
A way to cancel the hex out is finding the coin and shooting it.