These are Climbing Taiwans 304L welded rappel rings. What sets these apart from other welded rings is these are solution annealed to improve corrosion resistance, which helps to homogenize the structure, dissolve any carbides formed during welding, and to address problems that arise with welding. The welds are also ground down to make it traceless (and helps with ring rotation for even wear). They are also passivated for additional corrosion resistance. 

These have laser markings but are FAINT.  CTW doesn't like to laser after all the treatments. Laser-etching ~burns the surface, and consequently affects the corrosion resistant where the font is. They prefer passivation to be the last process. It keeps the rings clean and tidy and makes sure there's no contamination on the surface.