And I had a talk with them once on this exact topic. Among them, "the black safe" is an euphemism for the worst case scenario for the company. Nobody they asked exactly knew what is inside, but some people were instructed decades ago that in "worst case scenario," men with military training should open them with code that will be provided, without anything specific said on what will happen next. They said that judging by construction, they look exactly like a something for explosives storage.
I once had my dream of working in semi industry after being fascinated with electronics from early years. I studied physics and electronics engineering by myself like hell through my late teens, and had mentor who connected me with companies in Taiwan, and I almost got my leg in a Taiwanese fabless, though only in an "office bellboy" position.
Despite all of that, and me having a letter of recommendation for NTU and preliminary approval in Nanyang, parents sent me "to study businessy things rich people do"