NOS super sport grille emblem part # question

[Fast67VelleN2O]

I have an NOS SS grille emblem here, from what I believe to be 71-72 Chevelle. The box has one part number on it, 3991036, but the emblem has a different number cast into it,3987006. So what do I really have here? Is it a revised box number for the same emblem? Any help is appreciated.
Thanks,
Matt

[SS427]

I have the exact same NOS emblem and box here and that is exactly the same two part numbers that I have. It is in fact for a 71-72 Chevelle.

[Fast67VelleN2O]

Thanks!