Niobium speaker, maybe. 
This speaker is sold as a "600W Niobium Car Stereo Tweeter".  I'm not sure what the 600W means: Surely not 600 watts, which would instantly fry the poor thing.  I'm also not sure what the niobium in the name means: If there's niobium in there I sure can't find it.  Ah well, at least it was cheap. 
Source: eBay seller caraudiosupply 
Contributor: Theodore Gray 
Acquired: 1 May, 2004 
Price: $4 
Size: 1" 
Purity: 0%
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