It seems legit but it's just your basic Les Paul Custom Silverburst of recent. It will have a Richlite fingerboard, 490/498 pickups, etc... The 1894-2014 back cover plate is something Gibson used on alot of the 2014 models. It's not a rare guitar. Gibson did not make Les Paul Customs in 1894. The back plate went on many different models in 2014 as a anniversary to Gibson guitars, not to the specific model guitar.
So, in reality the back plate 120th anniversary(1894-2014) really means nothing value wise other than stating it is a 2014 model.
I have a Gibson 2014 Skinnerburst that has the same 1894-2014 back plate.