[Helleri]

For the dark scales, horn is not that thick, likely hoof.

[edited to cut out what I wrote previously. And to say that I don't think the lighting in the pictures is good enough to make a judgment on whether the white scales are ivory, bone or some other material. Pictures with high ambient lighting and no flash would be ideal]
The inlays on the butt are almost certainly enamel (even if the scales are ivory or bone). How flush it is and the fit of the inlay is too perfectly conforming to the hole in the horn to not be enamel.

The bolster/chape/grip is not silver. Silver does not oxidize red. That is steel.

[edited to add additional information below]
For helping to identify the white scale material:

First test:
Rub it vigorously with your thumb until it is warm. Bone or Ivory will smell strongly of burnt hair when rubbed like this.

Second test:
eat a sewing needle (you will want to hold it with pliers of some kind) over a flame until it is red hot. Touch the hot needle tip to one of the scales. If it burns at all it is not ivory. However bone will burn (leaving a blackened pin hole and likely with a small wisp of smoke that smells strongly of burnt hair).

Precautions with second test:
There is tiny chance that one or more of the scales could be a replacement/repair piece. If that is the case there is a possibility that it is made of bakelite. Which is a very early form of plastic and is highly flammable. So you will want to have a cold damp rag on stand by. If you see flame...drop the needle and the thing holding it immediately, grab the rag and press it hard against the test area quickly (bakelite can explode)! The chances of this are really really slim...but better safe then sorry.

If it does burn a tiny hole you can repair it by first cleaning the hole with a water dampened wooden tooth pick, then using a very high grit file (like those used for filing finger nails) you can get a little white dust off the edge of one of the scales. And after applying the tiniest dot of super glue (liquid form not gel form) to the hole with a needle tip you can wipe the white does you got into that hole. This should make for a seamless repair if it turned out to be bone.