The house I was raised in as a child in Niagara Falls, NY was built in
1928. NO K&T wiring when we moved in in 1941, but I believe there
might have been. Screw type fuses in a box going down into the cellar.
Electrical boxes, IIRC, were octagonal steel. There were a few of the
screw type outlets with a little metal flap. I stuck my finger into at
least one! Switches were dual push button type. Original service
couldn't have been more than 50 amps. I believe it was upgraded to 100
amps at one point when we lived there. Only major early electrical
appliances were an electric stove and refrigerator. Later, we added a
washer and dryer, which I remember required additional wiring. That
might have been when the 100 amp service was added. I have been back
to the house recently, and they have 200 amp service, and a LOT of
rewiring has been done.
My grandmother's house in Kansas, built in 1903 was K&T, later
refitted to armored cable. The house was fitted with gas lights, and I
assume some of the pipes might have been used for electrical conduit.