Jim, thanks for the kind words and welcome! It's good to be back (I did pop in from time to time, though). Excellent observation on the bone/ivory hilt. Of course this feature bears mentioning or, although it doesn't absolutely establish naval use, it is an extremely common feature to these dirks. Rob, don't be upset if it does turn out to be bone and not ivory. This material is far more likely to be what the average Confederate would have been able to get hi hands on. The crossguard/fennials bothered me at first with their slightly modern "sink knob" look. Then I remembered seeing a British piece with a rather ridiculous-looking crosspiece resembling flattened spoons! Here's a French piece, I think you'll see the similarities to yours -
www.antiqueswords.com/fnd1.htm
So...I stick by my (our) assessment. Rob, you can also check out Naval Swords by P.G.W. Annis ( 8 examples/pics of earlier styles, but same patterns), Naval Swords and Firearms by May/National Maritime Museum press and Navies of the American Revolution by Preston,Lyon, and Batchelor. Gilkerson's book, as Jim suggested, is an excellent resource.