He is clearly talking about IOUs of bitcoin, and you can tell from his mention on fractional reserve banking. What he probably imagined is a digital initiative of a gold standard. Banks used to provide IOUs of paper money, that were redeemable for gold; I understand it by the emphasis on nationalization of money:
Bitcoin backed banks will solve these problems. They can work like banks did before nationalization of currency.
(Before "nationalization of currency", there was gold standard.)