Maybe a training cobalt-60 source. 
This item was sold as a training simulator of a technetium generator.  It isn't.  There is such a thing as a technetium generator, but they don't look anything like this.  Instead, it's possible that it is a training simulator of a cobalt-60 gamma ray source or thermoelectric battery core.  But that's just guessing: The only thing I can say for sure is that neither the core nor the shield are made of anything but ordinary steel, and they are totally non-radioactive.  Any ideas, let me know. 
Source: eBay seller aztecjaguarwarrior 
Contributor: Theodore Gray 
Acquired: 20 August, 2003 
Text Updated: 11 March, 2007 
Price: $15 
Size: 3" 
Purity: 0% 
Sample Group: Medical
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