What kind of wire with three, not four (or two) twisted pairs?

Question

Cables and wires

In a rented apartment, when trying to connect to the Internet, this cable was found sticking out of the wall:

Instead of two or four twisted pairs, it has three. Can this be at all? And how to connect it in this case?
It was not possible to get an answer from the owners, because the repair was done a long time ago and no one remembers what the builders laid there in the walls. Next to this cable, a normal network cable with four pairs comes out of the wall, which was easily crimped and works fine (gives Internet to a network outlet in one of the rooms).
In addition, I managed to take a picture of the marking of this strange cable:

Apparently, this is really an ethernet cable, but ... without the fourth pair!
Who knows what it is? Can it be compressed? And How?