If the latter, try the pointed tip of a small butane soldering iron .. make up your own dot pattern/code .. barely have to touch it to make a nice little dimple.
Would work in low/no light situations too.
In this particular case, metal. But my question is general, because I had no clue. I’ve already gotten some great ideas. Thanks, everybody.
You bet. I did that for all my personal commercial kitchen equipment when I was in culinary school. Some barstid stole one of my bowls during the pastry practical exam and I found it because of the 'S' (3 dots closely spaced) that I had in everything I took to school.
I dumped his exam in the trash, and retrieved my steel bowl. Chef instructor watched the whole thing and I pointed out my 'mark'.
He failed. I passed.
Don't take my stuff. It's marked so I can find it in the dark.
/johnny