When this was installed in 1937, they used 1 1/2" nips to connect from one box to another, back then they din't use bonding locknuts or bushings, so the entire system is all loose bonding, dependant on pipe and locknuts, i think we do a better job of bonding in todays installations.
I really enjoy looking at pix of old installations such as this. Things have come a long ways, with modern inventions such as wire gutters and circuit breakers .
I have a panel in my collection, very much like the first four shown on that long wall. The panel is typically sealed by the POCO, and inside there is a single 30 amp main fuse, an EXO switch, and also a small knife switch inside the box - I presume to shunt the meter out of the circuit for testing or replacement. The customer's fuses (all two of them) are in a little "appendage" on the bottom of the panel with a little door that swings up.
It would be interesting to know what is in the main disconnect switch .