  Tungsten carbide car weight. 
Small (1" square) weight made of tungsten carbide and meant to be used in Pinewood Derby (model) race cars.  I'm not clear on whether that would be considered cheating or not. 
Source: eBay seller dlafew 
Contributor: Theodore Gray 
Acquired: 2 April, 2009 
Text Updated: 7 April, 2009 
Price: $10 
Size: 1" 
Purity: 90%
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