Hello I am not sure but I think it's a tactical sign. I have a yellow rectangle with H05 on my M152 it's on the 2 doors under the serial number, and at the back of the truck on the lower left corner of the door. 
 
But I dont no what it means !!!
		 
		
		
		
		
		
		
			
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				1953 Dodge M37 cargo 
1953 Dodge M37 radio truck 
1954 Dodge M37 costom 
1954 Dodge M152 communication 
 
If it doesn't exist anymore make your own
			 
		
		
		
		
		
	
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