|Tungsten spark plug.
Or at least, a spark plug made by a company called Tungsten. I don't really know if there is any tungsten in any part of these spark plugs, but I'll eventually test them and report what I find.
The most interesting thing about this sample is that not just one but two people would be willing to pay a minimum of $40 for a single rusty old spark plug (it takes two people to drive the price of an auction up). I'm not sure why I was willing to bid that high, and I certainly have no idea why the other idiot was, but isn't it wonderful that eBay exists to allow the exchange of a million people's junk into a million other people's treasure!
Here's an interesting article about different elements in spark plugs.
Source: eBay seller foos15
Contributor: Theodore Gray
Acquired: 12 November, 2002
Text Updated: 29 January, 2009
Sample Group: Spark Plugs