Lucky Coin

Special Ability
The extra damage bonus chances are shown below:

7 = 30% 77 = 50% 777 = 10% 7777 = 10% (if evo'd, otherwise 777)

The drop rate increase ability is based off total damage done, so adding Lucky Coin to your Challenge Dungeons team will provide it with an extra source of damage outside normal dungeons.

Token Improve
You can use a Pet Token to give Lucky Coin a class bonus for the Rogue class of 1.28% per CL. It will also further improve its Assassin bonus to 2% per CL.

Combined with Coin's drop rate bonus that already comes with evolving it, class changing Coin to Rogue makes it a very powerful pet for farming materials.