Use 'inauthentic' to describe art or items that are not original works but copies. This sculpture is inauthentic; it's merely a replica.
Pro Tip 2/3
Consumer Caution
'Inauthentic' signals to consumers that a product may not be trustworthy. Be careful when buying online, as the goods might be inauthentic.
Pro Tip 3/3
Authenticity Value
'Inauthentic' suggests that there's high value placed on authenticity in that context. Collectors scorn inauthentic memorabilia as they value true history.