Note: This is an outdated article, the methods given and even the gun to get has been removed from the game. Please do not necrobump the comments section.
Here is a tutorial on how you can get the Automatic Peacemaker in just one hour!
Method 1: (Outdated of 8.0.0) Players can go on Survival and kill waves of monsters and receive .
Method 2: Go to Time Survival and make a server. Lower the player limit to 2 only and DO NOT lock it or else you will not get coins. Once you hit 200 coins leave the match and let the other player take care of the rest of the monsters.