Thanks, Gents. Rich, the inspiration comes from a rifle that Wallace Gussler has. One of the coolest I've seen. It has a plain brass patch box, but you can see where the dove tail on the butt piece was filled in. Anyway, that's where I got the idea. There wasn't any (as I can remember) carving, so that was all my "add ons". Yes, there's a pin that secures the butt piece tang.
Mountainman, the stain is Aquia Fortis. 75% nitric acid, diluted with 6 parts water / 1 part acid. I added a chunk of metal off an old horse drawn manure spreader, and let that dissolve for about a day and a half, maybe two, can't remember for sure. What's left of the metal is taken out, and the acid/water mix is the stain. I apply the stain with a fine scotch brite pad, allow to dry, then blush with a heat gun.
Cheers,
Ed