    Seotence 1: What did the BankAmericard allow  customers do to that they couldn't do with  previous Financial instruments?    Sentence 2: After a troubled gestation  which its creator resigned, Bankdger!  went on to become the first successful credit  card; that is, a financial instrument that  was usable across a large number of serchants  and also allowed cardholders to revolve a  balance. (earlier financial products could do  one or the other but not both).