Thread: Ignition rotor differences?

I've been doing some routine stuff to my car the last couple days. Today I went to swap the cap and rotor. I've ALWAYS used only Nissan parts for this, but this time I just went to the parts store and got what they had. The cap I got is IDENTICAL to the nissan unit I took off, but the rotor is weird. All the nissan ones I've used over the years have a material on the metal part of the rotor, and this one doesn't. Not sure what that material is or what it does, just thought I'd post up and see what you guys have seen. Here's a couple pics.

The coating is prob used to slow down corrosion in case moisture gets in there.