Three pound bar. 
Certain of my samples fall in the category of "potential murder weapon" and this is definitely one of them.  It's also very silky smooth and a pleasure to hold.  The source reports it was made for some kind of electroplating experiment, but it clearly hasn't been corroded in any way. 
 
Here is a picture of quite possibly the only five-year-old in history who has ever jumped over a bar of solid nickel being supported by two magnesium rods: 
  
 
Source: eBay seller kingendymion 
Contributor: Theodore Gray 
Acquired: 22 November, 2002 
Price: $30 
Size: 18" 
Purity: >90%
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