I should perhaps clarify why I suggested Egypt, not as an overall source of the dagger, but just of the enamel cap.
To my eyes the entire thing could be a local imitation of a Ottoman style dagger, somewhat like this one:
http://www.christies.com/lotfinder/l...jectID=4363052
In a Sudanese context of course the potential for this sort of influence is ripe during the 19th century.
This link for the blade:
http://www.vikingsword.com/vb/showthread.php?t=1139
May prove interesting.