My understanding is that the 'C' refers to 'coarse' which means that the paint has a coarse (or larger size) metallic flake to it - Not sure whether the straight Fer 101 has a finer metallic flake in the paint but thats my guess. I am not an expert but I have read this elsewhere.
For 1980 and earlier, 'Argento Metallic 101' isn't listed - the closest PaintScratch show is 'Grigio Metallic 700'. Does anyone know if the 1970s cars' "silver" wheels are actually gray/grigio? TIA
Grigio is not correct. I would go with the 1981 silver. That is the oldest silver I could find on paint scratch.