Why would you want to cheapen your gun by coloring it with cold blue? Why would you want to hide or polish off the character that took 80 years to acquire? Enjoy it as it is... used but not abused. Very lightly clean it and oil it to preserve what is still there and to prevent rusting. Then take it hunting with low pressure loads and add your own share of honest wear. And when you and the dog stop and take a breather, you can look at it and think of the hunters who carried it before you, and the days it spent afield, and the game it has taken. When you are out hunting with your friends and their shiny pumps and autoloaders, smile and know you have the coolest gun in the group. Then when you are too old to hunt with it anymore, pass it on to someone who will appreciate it just the same.
