MelvinBucks
MelvinBucks are an investment commodity/currency created by clipchip under the name of Melvin3000. They are simply signed books stating their value, made to be the equivalent of a banknote. Due to the mechanics of signed books, it is not possible to copy them without the 'Original' text being changed. MelvinBucks that are not 'Original' have no value.
clipchip has spent a lot of time trying to sell them, and convince people of their value, promising that their value is nearly guaranteed to go up over time. A lot of people have been convinced by clipchip that they have value, and have therefore bought them. It is unknown how many are in circulation, and whether clipchip is actively minting more, or how frequently he mints more. Some people worry that MelvinBucks are merely a pyramid scheme.
They are not to be confused with the quarry investment, run by Quint and others.