Extreme tolerance parts.
BTW, Groom lake is to the NE of this photo.
BTW, Slide rules are great, but I gave those up years ago, I program all my CNC equipment in my head, I only use an editor to tell my machines what I want it to do. I'm sure all those cam programs are nice for people who don't really understand what a machine does but I know exactly what its doing.
Yeah...old timer....who knows what the....