Global Financial Instrument Service. The Security Master or financial instrument repository for all Global Middle and Back Office (GMBO) and front-office services. GFIN is a highly available service that provides the ability to create, retrieve, and query financial instruments. It also maintains accrued interest calculations for specific swap types, including total return swaps and credit default swaps. See also G3. See the Global Financial Information Service (GFIN) Technical Manual for details.