Hi Mosha,
I'm not sure, but would think it could be because the nose is carved from the outer layer of
cementum It also makes sense as it seems to be the most extreme part of the little guy. The transparency of the nose is what makes him so cute!
The "mis"-colored one in the bottom pic is the same material as the others, IMO. Sometimes ivory just ages more beautifully than in other cases. It's the same if you look at the walrus hilts above - some become golden and lustrous with time while others become grey and 'dirty' looking. I guess it depends on what kind of life the material has had and which kind of environment it's been stored in.
For this reason I in some cases personally find pieces of antler or bone more attractive than some pieces of ivory. I really love a warm and golden color and the aesthetic expression is more important to me in a piece, than the type of material.
I've found a new pekaka hilt in walrus ivory for you, but the photo is from a dealers page, so I'll send you the link in a pm.
We're not allowed to publically post pictures of stuff for sale, even if we don't reveal the source of the photo ...right?
Take care, - Thor