The Omani Work Knife.

[kahnjar1]

Here are three more examples. Though none are actually marked, they are likely from old european/british cutlery. The bottom item is made from a file.
Those used as a Khanjar back knife I believe to be called SHAFRA, and those which have their own scabbard and worn tucked into a belt or bandolier are called KHUSA.
I have shown the back knife scabbard as an information source.