Friedland Type 1 only has 3 terminals

I have this Friedland type 1. Firstly, is this suitable? I believe it is. The problem is it only has 3 terminals and everyone else seems to have 4. The picture shows exactly how it is now, before I’ve done anything, although it looks like the image has been rotated for no particular reason.There are two wires, one connects to the top left “0F” and the other connects to the bottom left “T3”. Nothing is connected to top right “1” and bottom right (unlabelled) doesn’t even seem to have a connection of any sort, there is no metal connector and no screw.What do I do?