I'm by my own admission, no expert... but was intrigued by your knife, its a beauty.
A quick search , showed some of Ed Kalfayan's (voting member Knifemakers Guild ) in the $300 - $800 range.
with two samples both coffin gripped, drop points in the spirit of yours calling $700 & $800.
Where would yours would fall ? Well it certainly, unique art of a fine craftsman now deceased, value is in the beholder and what one was willing to pay, I'd bet plenty !
"Mastodon ivory at all period correct ?"
well it's 10,000 years old , Species was discovered in the 17th century ...
The design of your looks on the lines of 1830-40's ....
Was it use ? why not ? used a lot ? , probably not ? On the other hand its
way more PC than say Corian® , faux Ivory, or many of the exotic wood laminates.
I am envious , and you have fine heirloom there, you have every right to be proud...
Congrats on your Uberti too ...