At what point did the better part of all brake rotors come from china?

[JeffP1167]

Also a long that line of question, I have some brake rotors from the rear of a 90 vette that appear to be original GM parts due to the GM looking numbers. Would these be the same size rotors as a ZR1 has? Originality wise are these worth anything? Or are they probably just china castings anyways since they were on a 1990?

Both are marked 10097655

 

[Twin_Turbo]

J55 and JL9 both use the 12" rear rotor with that oem part number. Those were on a ZR1 also.