Salaams all; It is not uncommon for Omani Khanjar parts to be interchanged. This is quite often done at random and over a number of years. I am not aware of any Khanjars that adopt foreign countries weapon parts even if in some cases the weapons are quite similar for example those of the Asir region and their daggers which are worn on both sides of the Saudia / Yemeni border. It simply isn't done. The closest Omani weapons to those of Yemen are to be found in the Dhofar region whose capital is Salalah. Often Omani Khanjars taken there have changed quite dramatically from their original configuration but careful detective work can unpick the mystery. Here is a Khanjar which I am including in this thread because it is in fact Omani. With it are other Omani dagger types from which parts were probably taken.
The first picture courtesy Forums http://www.vikingsword.com/vb/showthread.php?t=16834
by Khanjar 1 shows a remarkable Omani Khanjar chopped and changed down the decades and very much the style of Salalah Jebali weapon..This is a classic in its own right.
After that in no particular order are likely style candidates from which parts may have been obtained or chosen perhaps in the silversmiths shop or from pieces in the owners domain..and a bit of a punt for the prehistoric beast that provided the horn.
Ibrahiim al Balooshi.