|Broken gyroscope sphere.
See the sample above for a detailed explanation of these spheres. What makes this one fascinating is that it's cracked in half, allowing you to see just how thick the walls are. From holding an intact sphere you would think it must be a paper-thin, very delicate ball, because it's just so light. But with a broken one you can see that it's actually quite substantial: Beryllium is used for these sorts of parts precisely because it's so incredibly light weight.
Source: eBay seller spatial-one
Contributor: Theodore Gray
Acquired: 12 May, 2004