It seems unlikley its actually NOS, (as in new and never put on a car.) Is it black coated or painted?
When you say coupe do you mean bumperpad or 87-88? Or do you mean rear roof clip?
The bumperpad cover is common, (though NOS would be rare) still not very seeked after so the value would be less.
[This message has been edited by 2.5 (edited 08-04-2014).]