On the guns I build, mostly Civil War period Military types, I want them to be as historically authentic as possible.
I chose a cartouche as much like those commonly seen on original firearms. These can vary greatly but a common type is a rectangular box with rounded corners, about 1/2" long by 1/4" wide, with the Inspectors initials in script letters inside the box.
I chose my own initials (BJT) to stamp the stock in the correct location for that firearm.
This is just a method I chose to use for the arms I built.
My best,
Blair