Lovely looking Khanjar!  
I do notice though, that   the majority of splits seems less to do with age & more with  way, that  at the time of manufacture was unseasend,fresh or green ivory  which then split  as it shrank during drying on to the small decorative & grip improving nails, in the pommel/end grain area, with the splits then extending logitudualy,as it shrank further .
Perhaps Ibrahim can tell us when fresh rather than seasoned ivory became popular for Khanjar hilts in Oman?
I would assume traditionaly seasoned or dry ivory was prefered?  
 
Spiral