I served on two nuclear submarines during the Cold War. We did carry gold, firearm, and antibiotics.

They weren’t in a vault, though. The gold was carried, or worn by many individual crew members. I’m not talking about bullion, but jewelry.

The firearms were secured in the Small Arms Locker. We carried a small armory of M-16s, M-14s, short barreled shotguns, and a little ammo. The firearms were for physical protection of the boat while in port, or for limited protection for evolutions on the surface. Access was strictly limited to a few officers.

The antibiotics, along with all the other drugs were stored in lockers scattered all over the boat. So were all the spare parts and all most stores. There is a small storeroom, but it wasn’t enough to hold everything.

Those items were never intended to serve any other purpose than to protect the ship or her crew. There might have been some idle speculation about what would happen if there were some sort of nuclear event, but there was nothing official. Hate to ruin a perfectly good conspiracy theory, though.