Appraising a bank building
I would look at the neighboring land uses and anticipate the most likely user for the bank space. If there are comparable bank branch sales in the neighborhood, the answer may be easy.
If the branch is at the best corner in a prosperous, growing community, maybe it can still be reused as a bank building. A lot of older bank branch buildings are oversized, however, because they were built before the age of ATMs and on-line banking. In such a case I might look for bank branches that sold and remained as bank branches, but also make strong size adjustments for superadequate space.
Unfortunately, with all the technological advances in banking, most branch buildings are obsolete for banking purposes.
In office districts, bank branches often get reused as office space by realtors and stockbrokers, and I might appraise the bank branch as an office building.
Branches in low income neighborhoods often become chicken shacks and used appliance stores, and I would value the bank branch as a low-rent retail building.
In high-rent retail areas, older bank buildings often get reused as classy restaurants, and I would probably appraise it as a retail building, too.