Smoke detector circuit board. 
The circuit board inside a cheap hardware store ionization type smoke detector, with the ionization chamber removed so you can see the americium button inside. 
Source: Hardware Store 
Contributor: Theodore Gray 
Acquired: 1 May, 2009 
Text Updated: 2 May, 2009 
Price: $3 
Size: 3" 
Purity: <1%
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