In the 50's we had metal boxes and when you pulled up on the cover to remove it two ceramic/copper tipped fuses could be pulled to disconnect. My granddad would pull the fuses when he had enough of my siblings talking on the phone . If he left the house with a fuse, my brother would put two forks in place of the fuses, so they could talk.
It's pointed out (with older phones) to take phone off the hook in another room, before working. I don't know about modern phones (digital/wireless).
I have the newer box for the disconnect as you mention. Labeled on the box - "Customer Access" .
-- Oren
"Well, it doesn't happen all the time, but when it happens, it happens constantly."