This easter egg works only in Team Deathmatch or Squad Deathmatch. When spawning in the russian side, going north, in the corner of the map (SouthWest) there is shop like building with 2 small walls. Shooting the left one with Rocket Launcher shows up small room with M4 Sherman and 3 posters (PC/X360) and 4 on PS3. The Battlefield 1942 themesong can be heard.