Hey Jerry my car is standard interior but is a Z23 interior (could the chrome knob be part of Z23?) and my car had the chrome metal knob. I am almost certain its polished aluminum from factory because I see no chrome remnants anywhere and aluminum polish shines it right up like new.
Only 1 door had a knob other door knob is mia. I have had this car for almost 20 years and I am pretty sure it has original doors and although it is possible someone could have put metal knob in it before I got it. Anyways they sure look good to be so old after polish.