CI air cleaner, how do I tell NOS from repop?

[SOM2001SS]

I don't know enough to be able to tell an original piece from a reproduction, so please help me. My friend wants to sell me a cowl induction air cleaner assembly for my 70 Chevelle. This is the base, metal ring, and lid. Should there be part numbers on them? I don't see any. He is quite knowledgeable and has told me that he believes the base and metal ring are NOS and the lid is a repop. I trust him but want to know how to tell the difference. I could post pics if necessary. Thanks.