AN/USQ-20 (NTDS) with access doors open showing electronics module assemblies. Each of these assemblies is a removable unit containing a couple hundred 2 inch high by 3 inch wide single sided circuit boards of Diode-Transistor Logic, two transistors per board. Every board is encapsulated to protect it from humidity and salt. This was a Navy shipboard computer and thus is built like a "tank"!
I took this photo in the Computer History Museum in Mountain View, CA.