A few projects related to the T95 Medium and Chieftain tanks actually existed during the Cold War, so technically the in-game T95/FV4201 Chieftain isn't entirely fictional, or at least the idea of
World of Tanks - new year tales - Chieftain T95/FV4201 fate - MMOWG.net
WoT T95/FV4201 Tank Resin Kit – ResinScales
T95/FV4201 Chieftain - INVINCIBLE - World of Tanks - YouTube
FV4201 Chieftain/90mm Gun Tank T95 Hybrid - Tank Encyclopedia
T95/FV4201 Chieftain - Ratings, Equipment, Crews, Field modifications, Reviews, How-to play | Skill4ltu Index
World of Tanks 1.9.1 - T95 / FV4201 Chieftain - new 3d style - MMOWG.net