The two seem to be pretty much versions of each other, with (shades of matulis/talibon, but don't ask me for examples, please!) intermediary forms. 
Tim, are you saying the spacers are always/traditionally zinc?  I've taken ones I've seen for lead, and they seem to be composed of layers of almost foil-like thin-ness.  Mind you I wouldn't recognize unmixed zinc......so what's the deal?
		 
		
		
		
		
		
		
		
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