Re. marking of laser cut parts – 

In my experience, when working with laser cutting and engraving, it’s standard to use separate layers in your DXF file—one for cut lines and another for engravings like part numbers. It’s also helpful to include a technical drawing with your other files. Most manufacturing companies are familiar with this setup, but I always try to communicate the requirements when placing an order. I know that Xometry has a notes field when you quote your parts, you can add this info there.