I was surprised to see, in a bank built in the early 1960s, a safe-deposit vault door with a single bolt at the top, none elsewhere. It feels a bit minimalist though the full-height hinge certainly adds something. On the other side of the room is a second vault with perhaps 10-16 bolts (I try not to stare).

Was this fairly common? Still? Any comments on perceived security? I assume it had to meet UL and industry standards.