User blog comment:DawnShepherd/Gmod Portal 2 prop/@comment-67.168.18.32-20130516074816

Portal 2 still uses the Source Engine (Garry's Mod also uses the Source Engine), Even though Portal 2's Version is more updated than the GMOD Version of the Source Engine. The creator must've imported the models from the Portal 2 Branch of the Engine to the Garry's Mod engine (Half-Life 2: Episode 2)