Ihave a 6 inch sperm whale tooth I found in my aunt's attic.About 100+ years. worth, legality, etc?

Sharp point, sawn bottom. 2 " 1 mil. drying crack, unpolished. Would make great scrimshaw pc. Hollows out to about 2 and a half ", then solid. Worth? Legality of sale? do I need to register it before attemting to sell? Sincerely, Michael Byrt