Apparently you can buy this tank on 25-26 April in the premium store, but the downside of it is that it has that inscription which makes it look *ahem* unhistorical:
The guys who will have the luck to attend at the WGL finals will get one for free.
Check it out here:
http://worldoftanks.eu/en/news/pc-browser/esport/the-grand-finals-check-in/