The structure and color makes me think of a hilt I have.
See this old thread :
http://www.vikingsword.com/vb/showth...ght=raja+abala
Ok, but which animal / define marine ivory ?
There are quite a lot of sea mamals that can provide teeth that are workable :
Sperm whale ? orca/killerwhale ? seacow/dujong ? Walrus ? Narwal ?