Here is a project I've been working on it's a custom engraved handgun slide.
I've seen custom engraving done on firearms before done with a laser or by
hand, especially with this level of detail. In this project I used a rotary
engraver a vision engraving and routing system
VE 810 engraver to engrave the handgun
Although it's a rotary engraver the method I used was diamond scratch
also called diamond drag.