Not finding any threads on how to tell if you have original or replacement rotors. I've heard something about whether the fins are staggered, but not finding any examples.
Here are mine, from an Oct 64 San Jose K code fastback. They have K/H on the bolts, but think I remember that service replacements could still be Kelsey-Hayes.
Also, the hub where the grease cap mounts is a little different on each one.
Thanks,
Rich