I'm sure some of you have seen the Rigby .303 I started my posting career here with. This is the other double rifle in my families collection. The folks over at doublegunshop.com said I might be able to find out more about who / when it was made. It's a .405 caliber. Grandpa shot a number of gaur and elephant with it. I don't know enough about proof marks or even where to look to find the information on a gun such as this. The words on top of the barrels are "A. Thonon" on the right and "Namur" on the left. My apologies for the poor photography. Any help or expertise you can apply would be greatly appreciated.
I know the butt pad is not original. The original had simply disintrigrated.

~Wes