I’ve done a little bit with cermark. I had a hard time taking photos of these and have very little extra time this morning. Unfortunately, the really successful attempts left the shop before being photographed, but I emailed and asked them to send me a photo, so I’ll post when I get it.
These results are with a cheap dog tag which says it’s stainless, but I have my doubts about the composition of the metal and it may be interfering with the results.
The first two attempts are the bees and they were done without anything at all. Just put in the laser at full power and relatively slow speed. The larger bee was run with one pass and as you can see has some areas that are dark and some that are lighter. The smaller bee was run twice and is a little out of focus, so there must have been some very slight shift. The color is great on it though.
I purchased Cermark to try to get more consistent color, but it marks well without it. The Point Remove logo was done with cermark but at a very low resolution (lines per inch) and did not turn out well.
The really good ones looked great and are gone.
TL:DR - Cermark works, but it sometimes works with nothing also. And Lines per inch really matters.