IGR
A retired Wargaming partnership that lent vehicles to players connecting from a partner internet club, for the length of the session.
Also known as Internet Game Room, premium IGR, Igrovoy.
The vehicles were reissues rather than new tanks: the same Maus, Tiger I or WZ-132 as the tech tree, priced at a symbolic single credit and only playable while the IGR status was active. The rental came with bonus experience per battle, missions of its own, and free camouflage, inscriptions and emblems that lasted exactly as long as the session did.
Wargaming never spelled the acronym out in English. It comes from the Russian igrovoy, "of play", after the tariff the programme ran under, which is also why the Russian reissue is named T-44-100 Igrovoy. The expansion usually given for it is Internet Game Room. The programme is long gone, but the vehicles remain in the catalogue under an IGR suffix, because the accounts that played them still carry those battles.