Paul Mayer tested several products that are marketed or reputed as products that are capable of marking on metal using a CO2 laser in this article.
Hunst Co2 Laser Marking Machine 40W Metal Tube 100~150mm Working Area,for Nonmetal Material, Leather Wood Plastic Fabric
Laser marking steel, titanium, brass copper and aluminum
Marking on Metal with a CO2 Laser
3 Axis Dynamic RF CO2 Laser Marking Machine - CO2 Laser Marker
CO2 Metal Marking Spray with a Laser
Marking on Metal with a CO2 Laser
12 Oz - BLI101 - Aerosol Black Laser Ink for Metals Marking - CO2 Laser - Fiber Laser - YAG, Durable, Permanent, High Contrast, Brilliance Laser Inks
RF Metal Tube CO2 Laser Marking Machine 30W for Wood Clothing Fabric Marking and Engraving - China Enclosed Cover Laser Marker, Laser Marking Machine
CO2 Laser Marking Laser Color Marking Machine – WM machinery