In past years a particular type of two-door commercial safe was common in grocery stores. A large fire rated compartment, for cash register trays and paper work, had a big square door. This compartment was usually on the bottom.
Large amounts of cash, like the day’s bank deposits, were kept in a small top compartment, which usually had a small round door. This high security money chest (usually TL rated) has a heavy plate steel body which is encased in about 200# of concrete.
A single outer steel skin encloses both safes into a single unit. If the money chest is on top the units are top heavy and tricky to move. Weight requires these double units to be placed on concrete floors.
These units fell out of favor about twenty years ago because the high security compartment is too small. In addition, it is difficult to fit round doors with electronic locks. Stores seldom want these safes anymore, so that creates an opportunity for homeowners: Used round door /square door safes are readily available at safe shops for reasonable prices. Protect your personal papers from fire in the fire rated lower part, while your cash, silver and gold is safe from burglars in the high security money chest.