Geocaching is a new hobby that is basically a treasure hunt using GPS. Geocachers, as they like to be called, follow their GPS to the coordinates of a geocache and look for a hidden container. The container usually has a small gift which can be replaced with another gift.
A geocoin is a medallion used as a geocaching gift. It will usually have a tracking number on the back that can be activated on the internet. Once activated, the coin can be followed around the world it passes between geocachers.
This colletion has over 130 geocoins from all over the world. Common geocoins sell for about $10 each on eBay, and the rare coins sell for more than $50, so this collection is good value.