The bracteates were usually called back regularly, about once or twice a year, and must be exchanged for new coins ("Renovatio Monetae"). For example, receiving three new coins for four old coins. The withheld 4th coin was called strike money and was often the only tax revenue of the coin mint-master. This system worked like a demurrage: People wouldn't hoard their coins, because they lost their value. So, this money was used more as a medium of exchange than for storing value. This increased the velocity of money and stimulated the economy.