I had a partial case head separation using a 1.8oz buffer

[Fess]

Back when I worked for a company that produced pneumatic valves and hydraulic lifters (lash adjusters) for the automotive market, the cross sections were done differently. The parts were immersed in a "puck" of thin epoxy resin, under vacuum (to eliminate air bubbles), then cut by a diamond-tipped saw blade. This gave a very clear cross-section.
I agree that many of the cross-sections of cases seen in the interwebs are next to useless.