[thecyborganizer]

I currently work in the laser engraving industry, and I can confirm everything you've said to be true. However, I wanted to let you know about some extremely cool technology that I had the opportunity to experiment with a year ago or so. Some companies have developed optics with adaptive focus that use liquid lenses to mark beyond a 10mm depth-of-field - see https://www.optotune.com/technology/focus-tunable-lenses for an example, and https://youtu.be/ss-tkXcClMk for a video of the system in action.

I still don't think it would work well for your purposes - borosilicate just doesn't mark well, and you'd need to start with an accurate 3D model of the object - but I hope you enjoy the video!

(And thanks for writing the book!)