Please see
The Omani Khanjar. at
http://www.vikingsword.com/vb/showthread.php?t=14878
As you rightly point out a lot of replacements are not unusual in Omani Khanjars where most of the visible parts can be switched … In this case you have a cowhorn hilt on the usual array of silver worked plate and stitched silver over leather throughout and a button with the Omani Crest on it suggesting made after 1970 when HM Sultan Qaboos took power.