While I can't zoom in to see the printing on the box, I'm assuming (?) that Jeff's picture is of a C5AZ Rear Speaker Kit. I say "assuming" because I have seen many C5AZ Kits, some with the speaker grill shown in Jeff's picture (which I'll call the "horizontal" or Right to Left slots), and many with the "vertical" (or Front to Back slots). The horizontal slot grills go back as far as 1959 (I believe actually to 1957, but I don't have substantial documentation for 1957), as shown in the first picture that I have attached.
My NOS C5AZ Kit, has the vertical slots (second picture attached), as does my C7AZ Kit (third picture attached). As the grills and grill trim were part of the Speaker Kit, they did not carry a separate Part Number, at least that I've been able to find.
Main purpose however, is to show the differences. Based on the fact that both appear in the C5AZ Kits, and I have only seen the vertical ones in the C7AZ Kits, would lead me to believe that the change occurred somewhere in 1965-66.
Bob
