What actually marks stainless steel?

A fiber laser (1064nm) marks stainless natively — deep engraving, black annealed marks, and on a MOPA source, real color via pulse tuning. A 2W IR module makes light jewelry-grade surface marks. A diode or CO2 alone: no.

The workaround products (marking sprays and pastes) let a CO2 leave a bonded dark mark, at consumable cost per part and with prep time. For a business selling metal goods, fiber is not an upgrade — it is the machine.