Definitively not affiliated with Nazi Germany. It was the SS who wore the Totenkopf (dead man's head or skull and crossbones if you prefer). And although they "borrowed" it from earlier ancestors, even back to them it wasn't fashioned this way (as pointed out) nor as crudely (also mentioned) and finally never in lead. Their devices were most commonly aluminum and sometimes silver. Also, I don't believe the ring shown above is correctly identified, which is common for folks trying to sell similar items.
I would agree that this was likely a biker/pirate novelty piece. There were other military applications over the years, Including the USMC recon battalions, but definitely not an SS piece.
Never the less, it had to fun to find!