That certainly looks like a trench knife made from a bayonet.  Looks great and I bet you would have to work very hard to get another one. I am not really a reader of WW1 history but I am unaware of Turkish trenches other than Gallipoli/Dardinelles as far as I know the other Ottoman fronts were on open land.  A nice buy.  Tim
		 
		
		
		
		
		
		
		
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