Ok, in your one picture I now see how it's worn off. I wonder if that's a common issue with the stator bolts? Seem to hear about the magnets coming off the flywheel most often.
This page is from the K482 and K582 Service manual - hopefully it helps.
This one:What coil and where did you get it? Over the years I have had to replace two and no idea why they got fried. I understand there are a couple or more with different ratings. I also never knew the answer to the polarity question. Thank you.