Thanks for the info on the rotor. I'll check but would probably feel better replacing it either way. The "AAU" is what - sorry!All of those wear parts should be replaced.
Test your alternator rotor for looseness-View: https://www.youtube.com/watch?v=Nqq_gS_i1yc
Find a good welder and have them weld up that crack, or you can clean it VERY thoroughly, dress it with medium emery paper, clean it again with denatured alcohol, then apply JB Weld clear epoxy and let cure.
The AAU is still re-usable, as long as the springs have good tension and the parts are not sloppy loose.
Sure enough, the spring is gone from the seal.