The local Target has two support beams that have one gray bell mounted on them. One at the front of the store and one towards the center of the store. The fire alarms the store has are red NH horns on the support beams and white RSS strobes on the ceiling tiles. What are those bells for?
Loading dock warning bells, perhaps? Local grocery store has one near the dairy and related goods, which is where the [un]loading area is.
Sometimes there will also be a doorbell button at the front for the employees who arrive before the store is open to get let in. May also be for that too. But not uncommon for the loading dock door.