A couple of good aluminum milling images I identified:
KOM Inner Surface
Image by Drummond Masterton
Searching straight down into the inner surface of the bowl. Extraordinary that the surface comes out of the CNC milling machine at this finish, no polishing needed.
Mill Transmission (Bent!!)
Image by nebarnix
Image by virginsuicide photography
Developed out of aluminium swarfs. Huge John and his little sister Louis