Coins are items found when opening Chests or killing other players. The drop is random from people you kill, but usually you will receive more coins from those who are higher ranked in bones. There are 3 types of coins, each with a separate value.
Gold Coin
The Gold coin is worth (3) and is the most rare. It usually only drops from high ranking players, or only a few will drop from the chest.
Silver Coin
The Silver Coin is worth (2) and is the second most rare. You may come across it when killing average players, however it is the most common coin when opening chests.
Copper Coin
The Copper Coin is the most common coin, and is only worth (1). You can acquire the coin from killing ay player, and it will drop from chests.