A rather lengthy overview of the coinage used in a particular game world. At first glance it might seem useless if your game isn't set in that world, but it doesn't take long to find some great information you could port into just about any game system. Instead of just using a standardized system of coinage, breathe a little life into your game's monetary dealings with new coins for each realm.
This guide sets up the predominate coinage as a base and compares other countries (or city-states) coinage to that base. Coins can easily be compared to US coinage for a real-world comparison as well. The author takes some space to explain alternative exchange systems and even why barter might be preferred in some areas.
Some designer notes and instructions for making alterations to suite your own needs are included, but I think most GMs could easily borrow elements from this supplement. After reading this booklet I plan on incorporating some new coinage into my game world.