I was working for a financial software house called ACT Financial systems. Their main product, Quasar was an investment management system written in Mumps. It ran on Digital VMS and Sequent (Unix) systems.
Along with the core system providing general functions and libraries of reusable procedures, the system consisted of many modules to provide various features to the client. These were sold and supported separately.
Whilst at ACT, I was involved in the support of many modules, providing support to clients such as Lloyds, Barclays, Midland (Now part of HSBC) and Natwest.