Electrolytic marking (simple or shadow)
Electrolytic marking is a chemical process that creates a thin layer of oxidation on the metal surfaces. Unlike screen printing, it can only be done in black and is totally permanent.
Silk-screen printing
From sericum (silk in Latin) and graphein (writing in Greek), silk-screening is a printing technique that uses silk screens interposed between the ink and the steel plates. It allows a safe ink deposit which guarantees intense colour that lasts over time, and an excellent opacity. The best affective visual.