Good day Beau, 
 
The little tank is the radiator overflow tank. It is usually missing off most trucks, as they get damaged or rust out. 
 
You are very lucky to still have yours, I didn't notice mine until I took the photos as I didn't expect it to be still on the truck. 
 
Cheers Ken 
 
Cheers Ken
		 
		
		
		
		
		
		
			
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				1940 Cab 11 F15  1G-8129F     
1941 Cab 12 C60L AIF L4710841  Middle East veteran 
1941 Cab 12 F60L ARN 45818 
1941 Cab 12 F60L ARN 46660 
1941 Cab 12 F60L ARN 51720 A/T Portee 
1942 Cab 13 F15   ARN 55236 
1942 Cab 13 F60L ARN 58171 Mach "D" Loading 
1942 Cab 13 C15  ARN 62400  
1945 Cab 13 C60L ARN 77821 
1941 Chevrolet 3 Ton GS ARN AIF L16070 Middle East veteran 
Canadian REL (APF) radar trailer
			 
		
		
		
		
		
	
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