Near the end, solo and Farina go to a metal locked door to try to get in. The door is made of several metal plates welded together. Moments later, when they return to them cutting a hole through the door, it's a completely different door made of just one sheet of metal.
Near the end of Act 1 when Eric Braden was installing the eavesdropping wall he mentioned "thousands of tiny transistors". But the circuit assemblies just had vacuum tubes which were easily seen as well as resistors and capacitors.