Banker's Bank

A bankers' bank is a financial institution that provides financial services to community banks in the United States of America. Bankers' banks are owned by investor banks and may provide services only to community banks. Leveraging positive economies of scale bankers' banks are able to provide many services to community banks that typically would only be economically available to large national or multinational banks. The advantage here is that community banks who use these services can in turn offer them to their customers, allowing these smaller independent banks to effectively compete with larger banks.
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bank that is established by mutual consent by independent and unaffiliated banks to provide a clearinghouse for financial transactions.

BANCA CENTRALE. BANCA DELLE BANCHE