"PC" is also commonly used to mean Publisher/Printer's Copy. Again, like others, have seen this many times in other (far smaller run) limited print runs; used for copies outwith the normal limitation number. Looks like AL's handwriting to me.

My copy also has a strange number, is it "0" or "o"?

I believe these are assigned after the limitation numbers? Someone no doubt will give you a correct answer soon enough, rather than me assuming I know! ?