I think Frank is correct that the original appearance wasn't quite so uniformly perfect. Although I'm generally an "originalist", in this case I just hated popping the lid and the first thing that caught my eye was a dingy, mottled, greasy, beat-up looking fan front and center in the engine. This is one case where I'll take over-restored vs. factory original. If it starts bugging me because it's too pretty I'll throw some cosmoline on it.

And Mark does do them with a clear ceramic coating so that the original magnesium is visible. He makes the coating opaque when the fan blades have repairs that need to be hidden.