  Large krypton bulb. 
This is a Sylvania K205PS25 incandescent lamp, said to be filled with krypton, and said to have a lifetime of 12,000 hours, which is huge for an incandescent bulb.  It must operate at a very low filament temperature, and thus be extraordinarily inefficient at producing visible light. 
Source: eBay seller maxiemumdeals 
Contributor: Theodore Gray 
Acquired: 8 February, 2009 
Text Updated: 8 February, 2009 
Price: $3 
Size: 6" 
Purity: 1%
 |  
  |  
 |  
  |