I have too many different power supplies and quite a few old ones I don't know which device they belong to. So I started engraving a label directly into the black plastic.
Normally I use my MOPA Fiber laser for this, but since I received my F1 I wanted to see if it is up to the task and I am quite pleased with the results.

I used the reference black acrylic settings for engraving the power supplies. For a whiter engraving you can spray a thin coat of satin lacquer before engraving.

Perfect focus is key when engraving plastics

IMPORTANT:  Make sure you are using a ventilation system as some plastics can create harmful gasses during engraving.