Indeed a cultural mix as David pointed out allready. 
I clearly see Nias people, a warrior from Timor if I am not mistaken (left of the Nias warriors), in the back to the right a warrior from Celebes/Sulawesi (if I'm right). 
The fourth man could be a negrito maybe? 
And also some people which are hard to tell exactly where they are coming from. Looks like java, sumatra, and????? 
  
I liked the image, and I stumbled on it on the internet. 
It was described as following: 
Original chromolithograph by Armand, Amsterdam from Nederlandsch Oost-Indie by P.A. van der Lith, published in Doesborgh, 1875 
  
I don't know who is Armand, but I try to find out yet... 
  
  
Maurice
		 
		
		
		
		
		
		
		
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