You should have posted this in the tinplate section, as that is where it would have had the most visibility.
As far as a wiring diagram, there is not such a thing, but I have worked on these.
first of all, your reverse unit should look like this
another view
A view without the square housing and reverse lever
The two fingers in the above photo and the center Y bar that they are resting against is the basics of the mechanism. The reverse lever, which is missing in the above photo, spreads one of the fingers away from the Y bar at the center, depending on its position.
Having working on several of these reverse mechanisms, I can tell you that they can be temperamental, with the reverse lever not always spreading the fingers properly. The reverse bar should cause 1 of the fingers to be touching only the reverse bar and the other touching the center Y bar. This causes an electrical circuit to be formed by the center roller pick up to the bottom of the field, the top of the field to the center Y bar to the finger that is touching it to the associated brush, through the armature, out the other brush to the finger and then to the reverse lever that is touching it, to the frame and to wheels and to the track. I have had to adjust the bend of the fingers to get the mechanisms to work properly.
As for wiring the reverse unit, there are the wire contacts that come out of the top (which are ultimately, the fingers topmost posts). There is also a wire that attaches to the center Y bar top post. The center Y bar top should be connected to the topside of the field. The two wires going from the top of the fingers go to the brushes, which may be finger brushes on the early locomotives or tube brushes on later locomotives.
Hope this answers your questions.
NWL
