To put it more simply--credit is a set of promises to pay; will those promises be kept?
Especially in banking, where the 'liabilities,' or promises to pay, are so large, and the time at which to pay them, if exacted, is so short, an instant capacity to meet engagements is the cardinal excellence.
All which a banker wants to pay his creditors is a sufficient supply of the legal tender of the country, no matter what that legal tender may be.

Different countries differ in their laws of legal tender, but for the primary purposes of banking these systems are not material.

A good system of currency will benefit the country, and a bad system will hurt it.

Indirectly, bankers will be benefited or injured with the country in which they live; but practically, and for the purposes of their daily life, they have no need to think, and never do think, on theories of currency.

They look at the matter simply.