They’re from the phones you see in old movies that you had to crank to talk to an operator, commonly used up until the 1950’s. I put my multimeter on one and it’s still reading 1.3 volts. The owner told me I can take the whole lot of them if I want them which I’m tempted to do just because I like to collect old junk but I probably drag enough useless crap home as it is.
I was snaking a 240 volt line up through the attic when I found them. Judging by the dust I’m probably the first person up there in a few years. The phone lines have been upgraded and rewired with all this older stuff disconnected and just left behind and forgotten about.
With how things usually go in such cases, when you disconnect them half the city phone lines will go down.