How about a dab of nail polish. Your choise of color.Could be used to mark differet calbers. And do your toes.
"When Government fears the people, it's liberty. When people fear the Government, it's tyranny."
- Benjamin Franklin
And if you don't like the color your wife can use it. It would be only normal here in the Gainesville Fla. Home of the law that allows men to use the women bathroom if they feel fem.