Easy way to get unknown coins.
The most easy way to get unknown coins is to memorize where the ads located. And if you already know where the ads can be found, You can skip the ads. How? By buying skip ads on the perks store but you don't have enough credit to afford it you can enjoy watching ads.
Always maximize the amount of ads to be skip or watch make sure don't miss anything
After watching all ads you can calculate how much unknown coins you collected, If you are not satisfied you can purchase some VIPs to get more unknown coins the high the VIP the more unknown coins to gather.
You can also get more unknown coins by pushing your chapters progress the higher you pass the chapters the more unknown coins you can collect.
After that you can enjoy crafting your unknown coins on the jeep safe.
As I know you can get higher grade of keys on 25000 unknown coins compared to the 2500.