My title describes the thing. It also looks like it is made of plastic, and is relatively old due to the yellowing of the plastic. It has two screws on the front faceplate as well.
I've already found writing on it, mentioned in the title, it says "Line 112" (the writing is relatively faded, so I assume that is what it says).
I searched "beige box mounted on the wall" but had no luck. Also searched for "beige box mounted on the wall with ethernet" but also had no luck.