What does screwed blued and tatooed mean?

The definition goes way back to early Tool and Dye Makers. After inspecting a finished manufactured or repaired part, the Toolmaker/machinist would

tighten all parts and screws (Screwed), Use Blueing a blue paint lke stain that stuck easaly to metal (blued) and, then put his inspectors mark through the blue paint with a sharp scriber (tattooed) The part has passed inspection, it's been screwed, blued and tattooed and ready for release from the machine shop.