I have 4 or 5 identical SS mags and I'd like to know which one is which for reliability purposes, right now I have some ugly nail varnish 'dots' on them but I'd like to do better?
Use an indelible felt tip marker the same color as the base pad. Write it on the pad. You may have to strain to see the number but it’s better than a bright colored numeral.
If you really want it done nicely take the mags to an engraver and have them tastefully etched.
IMO sharpies don’t last long.
Get a paint marker/pen
If you have a good hardware store , they should have them.
These had heavy duty paint and if you clean off the mag with acetone or alcohol first the paint will last a very long time and won’t wear off.
You may try a trophy shop to engrave them as that looks a heck of a lot nicer than a etching pen. I did the etching pen and wish I had gone to a engraver and paid the price. My Glock Mags I have used Cricket and done a stick on that has held really well, I did use a hair drier to help set numbers.