  Reed switches. 
These reed switches have rhodium-plated electrical contacts.  I don't know why rhodium and not gold, a more common contact material.  Reed switches work by opening or closing when a magnet is moved close to the sealed glass tube.  These are normally closed switches. 
Source: eBay seller virtualvillage-usa 
Contributor: Theodore Gray 
Acquired: 28 February, 2009 
Text Updated: 1 March, 2009 
Price: $0.30 
Size: 1" 
Purity: 98%
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