Tier 9 Unlock Token
Tier 10 Unlock Token
Unlock Tokens are used to unlock Tier 9 and Tier 10 progression vehicles that are under the dealership of Sophie Wölfli, Marat Shishkin, and Zhang Feng. This system was first made available along with Tier 9 vehicles' debut in November 5, 2015.[1]
When a Tier 8 progression vehicle from one of the three abovementioned dealers reaches renowned status (i.e. progress bar reaches 100%), a Tier 9 Unlock Token can be obtained and used to unlock one of the Tier 9 progression vehicles from the same dealer. An exception to this rule is the Leopard Evolution, which does not provide a Tier 9 Unlock Token at all. The same rule applies for unlocking Tier 10 vehicles: a Tier 10 Unlock Token must be obtained from a renowned Tier 9 progression vehicle in order to unlock a Tier 10 progression vehicle from the same dealer.
After unlocking a vehicle with an Unlock Token, it must still be purchased with 
Credits as with any other progression vehicles. The unlocking process is irreversible, which means it is impossible to backtrack and unlock another vehicle with the same Unlock Token.
The advantage the Unlock Token system is that Tier 9 and 10 progressions are not bound to specific progression lines or branches.[2] For example, it is possible to unlock the Tier 9 B1 Draco Tank Destroyer via the Tier 8 VBR Armored Fighting Vehicle, then unlock the Tier 10 XM1A3 Main Battle Tank via the B1 Draco from the same dealer.