Wiktionary
genuine fake
n. An imitation of a (usually) valuable object that is so good that it is, to all intents and purposes, identical.
Usage examples of "genuine fake".
Meg suspected that only Gran's restraining hand had prevented Dan from converting it into a genuine fake manor house, complete with battlements and towers.
His breath smelled like a week-dead skunk, and the stink clung almost as well as the odor from the Bazaar's famous Genuine Fake Doggie Doodle with Genuine Odor That Really Sticks to Your Hands.