I doubt that that grounded receptacle is 70 years old. Looks like the MDFB behind it has been replaced.
That type rust is normally associated with having been under water or having very high humidity shooting directly onto it for a considerably long time.
I've seen some real sheeiit holes in my day... everytime I see a really bad one, I think back and just shake my head and realize that I've maybe seen the worst I may ever see.
This week, I showed up to a foreclosure and the buyer met me there and told me that the electricity did not get turned on as had been promised. Anyway, he and I took a walk around and then inside the home....
Now, I can say (absolutely) that this one wasn't the worst, but I can say that it will make the top 20 list and that's pretty bad.
rr