Sometimes I get lucky and receive some for achievements, but it’s greatly situational. There are also events, like the current “Royal Navy”, which gives out tokens that can be used to buy these.
But the main source is coal, and coal comes from two “daily quests”:
The first needs you to collect some XP. That’s pretty easy if you have premium and +XP camo. “Pay to win” if you want to call it, but it’s in the range of $15/month, so it would be an overstatement. Every container has 400 or 800 coal.
The other is two consecutive literal daily quests. The first is trivial. The second needs you to win 3 games, with 1100, 1200, 1300 base XP. That wasn’t a problem with Shima. 50% winrate means 6 games on average. Of course Murphy says that you win in a row when you have lot of time and you lose in a row when you have time only for a few games. But now I’m maxing out the captain of my Grozovoi. I was very pleased with its performance in ranked against CVs and want to use it next season. However an AA specced Grozovoi doesn’t perform well in randoms. Ergo, winning with 1200+ base XP is rare. So I must play a lot to complete this quest.
However, do I really need that 200 coal?! Is it worth doing randoms after the third box is already gained? No. This is the message: you don’t have to complete every daily quest and get every damn reward. You can just do those that are efficient and leave the rest. My time is worth more than 200 coal.