Differences in the Duster shark tooth grill.

I have been doing some research on the Duster shark tooth grill and I read some other threads about them being molded in black plastic or silver plastic, and the different ways they were painted.
I have one that is molded in black plastic and is painted silver, but the fins are still black. Does that mean it was a 71 or a 72 grill, and is it from any special option package, such as a hood blackout treatment that some people have commented on. Thanks for your input.