Česká zbrojovka a.s. Uherský Brod = CZ
Lacking pics or a more detailed description and markings rundown, the shotgun sounds like it's a CZ shotgun, probably a model 581.
Does it have the CZ's Kersten locking bolt ? (A metal part pops/slides out of the action, to one side, when the opening lever is moved to open the barrels)
Does it look like this one ?