  Mechanical MagicCube. 
Mechanically (pyrotechnically) fired GE MagiCube flash cube.  Remarkably, these flash bulbs have no electrical contacts.  A thin tube filled with contact-sensitive explosive (I would guess mercury fulminate) leads into each bulb, and is set off with a sharp knock on the bottom.  
Source: eBay seller clinia 
Contributor: Theodore Gray 
Acquired: 2 April, 2009 
Text Updated: 7 April, 2009 
Price: $5 
Size: 1.25" 
Purity: <10%
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