I stumbled across this device while renovating the bedroom of my house. It is screwed into the wall. There is only one wire going into it. The wire has several small diameter wires inside the sheathing and those wires are connected to the device in some nontrivial fashion.
Is it something abandoned?
It's a beat up telephone jack. You can see the actual plastic jack off on the left, and there was originally a cover over the box.
It's a four-wire junction box (missing plastic cover) for connecting a phone or other customer premises equipment to one or more central office lines. It predates the use of phone jacks.
Other answers provide great info, just adding a picture for reference. At first glance I thought it was an RJ45 block, but this has less screws.
Image from https://www.commgear.com/allen-tel-4-cond-surface-jack-biscuit.html
