The Asteroid Belt lies between Mars and the Outer planets. Some of these rocks rival the size of poor demoted Pluto. Many Sci-Fi dramas (and a few actual farseeing mining/colonizing schemes) envision this region being the source of many rare minerals.
Nothing overly rare about this cache ... but there are a few trinkets, including a Coveted Doc Musketeers FTF magnet for the first Finder.