Much work has been done on software reuse "in the small" - objects, subroutines, and components. However, relatively little research on very largegrained reuse is available in the literature. This initial study of a large US-based banking institution indicates significant levels of innovative reuse of internally developed software, including reusing both infrastructure and applications across Internet, teller systems, and ATM systems, all with surprisingly little customization and rewriting. This study presents findings of the initial research, including the types and granularities of reused systems. A conceptual model to explain their success is proposed, addressing both organizational and technical factors, and next steps are documented.