Col

Col is the form of currency in the world of Sword Art Online: Project Eternity.

Methods of Acquiring
The valued currency of Sword Art Online: Project Eternity is gathered swiftly from boss battles, as they yield a large amount of valuable loot, but the loot is usually shared among all participants of the boss battle. Other methods of acquiring Col include killing monsters in dungeons or open fields, trading, and for orange guilds and players, ambushing other players and asking money in exchange for their lives.

Inflation
Because the value of 1 Cor is based on the drop rate maintained by the Cardinal System which is kept constant at all times, neither inflation nor depreciation ever happen in Aincrad.

Trivia

 * Cor is an abbreviation for "coin of radius", which most likely means "currency of Aincrad."