The feed plate also exists as plain metal (painted green) with a central ceramic feed-through insulator, 
 
The mounting (that one is Canadian and made of plywood with cork gaskets) was also produced in rubber (a variety of colours - I've seen natural (brown), white, and black examples). Post-WW2 they made them from pairs of stamped steel dishes, seam-welded, and used rubber gaskets as necessary. 
 
I think Tim Bell posted photographs of a selection of the types some time ago. 
 
Chris.
		 
		
		
		
		
		
		
		
		
	
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