Hi Howard,
Flitz is a poishing/cleaner paste - and in fact, is pretty good. It won't attack factory blue (use it gently, though)- but it sure can remove "cold blue" touch-ups which have been previously applied. I actually used the stuff on a shooter Luger - where some idiot had used black permanent magic marker to try to "enhance" the appearance of his "Looger"
Best to you..!
- John