just trying to add to MGM1251 questions and Chalky's answers. So...Forgive me if i'm behind the thread somewhat or the bit below is meaningless to the debate.
I have a scribbled note (and given time will find the source of the note to give due credit) that;
Matrix of Nashville (the company) made amongst other things, stampers for local pressing plants. And Nashville Matrix (in Italics) was the wording in their metal stamper. So it’s likely Nashville Record Productions Inc (Mastering) used those/that stamper(s). And we know Motown used NRP, as did Paula, etc.
I could be stating 'the bleedin' obvious' to many on here. Equally, I hope it hasn't unwittingly sent you down another rat hole, or