Spark Plug.
Lord only knows what else you could make the core of a spark plug out of, but this one prominently advertises the fact that it's made of copper. I got it to go with my collection of spark plug elements, which is surprisingly diverse, extending even to man-made radioactive elements.
Here's an interesting article about different elements in spark plugs. Source:Farm & Fleet Contributor:Theodore Gray Acquired:19 November, 2002 Text Updated:11 August, 2007 Price: $2 Size: 3" Purity: >95% Sample Group:Spark Plugs
