This is a machined beryllium missile part of some sort. Beryllium is extremely toxic in powdered form, but relatively harmless as long as it's fully intact. Making a part like this must be quite difficult to do safely considering the amount of very toxic beryllium dust and shavings that would be generated.
Source: eBay seller parker282828
Contributor: Theodore Gray
Acquired: 12 May, 2004
Text Updated: 18 October, 2009