The outside parts are from Japan, but the rest of the parts are all Western Electric. The WE Kit is F-56660.
After buying the "enclosure," you sent the phone to Western Electric or an installer came to your house to add the dial, network, ringer, transmitter, receiver, etc. This cost about $25.00.
The parts remained property of the phone company. So they charged you rent on the parts--$1.50 a month or thereabouts.
If you didn't want to continue paying rent on the parts, you could have the phone company remove the W.E. parts. There was also a program in the 1980s to buy phones you had been leasing; I would think this would apply to the inside parts of this phone as well.