This Encyclopedia explores the recent phenomenon of physical crypto-currency and the infrastructure that surrounds it. These are metal coins that reference various crypto-currencies of which Bitcoin is currently the most prominent. Many of these coins are funded with digital currency that can be extracted and used at will. Others are themed to celebrate the emergence of digital currency. The new hobby of collecting physical Bitcoin and related crypto-currencies has created an expanding industry in which dozens of companies and individuals create and sell their coins to a growing market of collectors. This work covers 57 such manufacturers. There is also a thriving trade in pre-owned coins. Physical crypto-currencies have become rare objects with the highest value sale to date reaching one million dollars on the re-sale market.