I could be wrong but I thought the PC stood for "Pneumatic Commercial" and that there was also a SC or "Solid Commercial". These referred to the types of tires on trucks. The SC's were charged a higher fee because of wear and tear on roads.
Like I said I am not remembering as I used to, you are probably right. I can't find that information anymore, I have to go by memory. There was several other types too, I have one for my CE and the plate includes CE just like the PC plates. I have seen BE too. I know that if you have two plates, in most cases you can use them all.
