Thanks to Babykim, EU.
Developer SoaRen on the possibility of converting gold to doubloons (RU Forum).
The transfer of gold from tanks to doubloons is possible, provided the following conditions apply:
1). Gold purchased by the owner (it is not essential what was purchased, essential is the act of purchase), (TN: i.e. bought for real money alone, or as part of a bundle;)
2). Not gold awarded as prizes, offerings or gifts (e.g., in competitions);
3). The minimal amount of transfer: 2,500 gold/doubloons;
4). At least one month of inactivity in the game where the gold comes from, (TN: i.e. have not played tanks or planes since at least one month;)
5). One transfer per account only.