Hi Marcus, 
 
What you have is a good old Kuba Ikul knife (+-1900-1920 is my guess). 
Check if yours have a cutting edge (I suspect yes). 
 
These knives are often partially blackened using a palm oil, like this one.. 
 
Most of the above examples are overcleaned or, not (fully) cleaned (leaving their patina). I wouldn't touch yours too much..
		 
		
		
		
			
		
		
		
		
		
		
		
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