Remember that most places source from several vendors and what may be mix X to one supplier is something else to another.
What do you mean by "... what may be mix X to one supplier is something else to another." ?
I wondered about that as well, I was under the impression that the "mix" numbers were a creation of Fair-Rite, and that the other core makers had their own mix designations...
Fair-Rite has its house numbering scheme, and it is NOT an industry standard.
What Is an industry standard is the color code.
Taiwan, China, France, they all go by color code.