when can you un seal the safe?
You un-seal the safe and certain stores lockers (bonded stores) after you leave port.
The ships I was captain of had one old .38 revolver with 100 rounds of ammo. A very standard setup on US flag merchant ships. Every time you entered port you declared one revolver and 100 rnds of ammunition.
I did hear of a ship where the master committed suicide with the ships revolver. That was the ship which then had a declaration of one revolver and 99 rnds of ammo.
Ships are allowed to carry more then that but that is based on company and or the master. We had a skeet shot gun on one ship.