Hello Russel, I'm thinking that the hilt material on your new gunong looks more likely to be tridacna than ivory or bone. Now this is based only on the photos you have posted and because of their quality I could very easily be wrong. In the second photo where the hilt meets the ferrule there is a gap and the color of the material that can be seen there looks too white to me to be ivory. Also the overall soft look to the material remind me of oxidized shell more than it does of old dry ivory. I would say that this piece dates to the first quarter of the 20th century. My congratulation to you on this very nice new addition to your growing collection of gunongs.
I'll be very interested to see new photos of it after it arrives and you have had a chance to clean it up a bit just to see if the metal on the scabbard and ferrule are silver of not.
Best,
Robert