Hi Dave,
I believe Dick is correct that the inlay is ivory. First, it seems to have streaks of brown throughout (at least on my screen), which tend to indicate ivory rather than bone. Bone typically stays whiter than ivory over time. In addition, I've worked quite a bit with bone inlay, and I can tell you that creating that intricate an inlay is very hard (although certainly possible) because the material is brittle. Ivory is a bit more forgiving. Finally, bone workers generally preferred cow leg bones (femur is the best) because it is very dense and strong compared with bone from other areas of the animal. If that inlay is made from 1 piece, it would be hard to find cow leg bone sufficiently large to make it. However, elephant tusk ivory likely would work. The exception of course would be whale bone (not baleen though), but I think the brown colors suggest ivory.
Again, thank you Dave for the photos. I've enjoyed them very much. I really think it is one of the best examples of rococo art I've yet seen on a gun and for that reason alone, it is worth study. The word "rococo" implies "shell-like" and the characteristics that distinguish rococo art from baroque and other earlier styles are asymmetry of design, use of stylized shell forms, and a feeling of lightness and movement. While baroque tended to represent forms naturally, rococo artists stylized and distorted them to create that feeling.
dave
