The only way you are going to know for sure is taking the whole thing apart and probably destroying it in the process. Fakes are so real looking these days.
If you really want authentic, you need to buy new directly from Apple.
This one is uff old,myb it is from orginal iphone 7/6 idk… my mom from her iPhone 7 (secendhand) have the same charger,but i am not sure this is why i am asking here :/