Epic thread Jack on this one.
Here's what Ken is talking about, an airsal piston I pulled with about 1500 miles with a textbook perfect break in on 30:1 dominator. The black on top was where the trans oil was getting sucked in through a bad crank seal, causing me to tear it down and rebuild.
Normally I don't take apart a perfectly good top end so I don't have a lot of these kinds of pics. Just took this one because it's such a nice break in you can see perfect even shine on the rings with no streaks or dull spots and a perfect clean skirt with the high spots just slightly worn down.