The dot economy is a slick emergent economy that is used in prisons as a form of real currency.
Alice buys a $100 pre-loaded MoneyPak card with cash at CVS. There are 14 digits on the back of it that now act as a proxy for $100.
Alice chats with Bob in prison and tells him the 14 numbers. Bob now has $100 available to him to spend wherever.
Bob makes a deal with Claire, the guard, to buy $100 worth of drugs. Bob tells Claire the 14 digits in exchange for the goods.
Claire then logs into her pre-paid charge card account and punches in those 14 numbers and $100 appear on the card.
The charge card is the bank, the MoneyPak codes (dots) are the currency.