In an attempt to prevent debasement of the currency by the influx of adulterated coins, the Hamburger Bank was founded in 1619. It was modeled after the example of the Bank of Amsterdam. Both these banks established a stable money of account. The Hamburg unit of account was the mark banco. It was credited in exchange for the sale of bullion or by way of credit against collateral. No coins or banknotes were issued, but accounts were opened showing a credit balance. The account holders could use their credit balances by remittances to other accounts or by drawing bills of exchange against them. These bills circulated and could be transferred by endorsement, and were accepted as payment. They could also be redeemed. This currency proved to be very stable.