What do the letters at the beginning of the Chinese RMB (CNY) serial no. mean? Also are the numbers just rand?

I know that the letters must stand for the diffferent places or companies that printed them but is there some sort of specific list that can tell you this? Also, the numbers after the letters... are they jsut random? or could one know what type of not it is based on the serial number itself





just wondering.... does anyone know?|||Just in order to distinguish the batches of print...