Described as a beryllium gyroscope sphere from a military aircraft. It's definitely not one of the classic light-weight gyroscope spheres: It appears to be solid, though of course still very light. No idea what it was really used for.
Source: eBay seller ohioidustrialsurplus
Contributor: Theodore Gray
Acquired: 10 January, 2006
Text Updated: 20 February, 2006