If you could submit photographs of the rifle and the horn along with any other pertinent information, there are many here who can help you.
The maker is a well known gun builder of the mid 1800s and his work is oftentimes very desirable.
It would be helpful to include data such as overall length, barrel length, type of ignition, (flintlock, or percussion) and anything you can provide regarding details to inlude, engraving, inlays, patchbox, ramrod and so on.
Do much the same with the horn, if you would,
Regards-Dick