The thing about molds is they changed factories, thus changing hands. Kenner used multiple factories, most in Hong Kong, but some in Taiwan and China to make figures. The reason coo changes occur is either the mold wore out and things like periods or even parts of the words themselves in some cases broke out. Other changes was when they filled in the coo, or changed the country completely. There are red snags for instance with parts of hong and Kong missing, there are figures with partial scars on the coo where they filled but didn't fill completely, there are many different and varying marks.
You can read more about molds and whatnot in some of the reference links here.
I have caviar dreams and McDonald's pockets