TWD: All-Stars Official Forum (The Walking Dead: All-Stars)

Easy and free way:

First increase your crafting level by making progress in chapters and vip level to get more key points during watching ads or skipping ads( there is some hidden ads including reseting cooldown time in training ground, reseting enemies in supply run, reseting strategy in supply run)

When you collected enough key point craft it to get the keys then open safes, better keys and better safe means higher chance to get unknown coins.

Note: if you open safes instantly you have even more higher chance to get unknown coins

So it short in 4 steps:

1. 1. Increase crafting level
2. 2. Watch ads to get key points
3. 3. Craft
4. 4. Get the keys and open safes
5.  
6. Second way:
7. XPLA game wallet and participating in in-game XPLA events to get unknown coins.