really rare, that you could become some type of famous person
Rare earth metals are an extremely reactive group on the periodic table. They are rare because they tend to react with everything, so are usually not found pure.
No but its better then nothing
Determine how many were minted, when and where and the numismatic grade and, last but not least, the availability of the coin for purchase
Not all rare moshlings you need rare seeds for but if you do want rare seeds for a particular type you have to become a member and go to the port.