Wiring diagram forward/reverse switch for a 8502 Steam Engine

The 8502 has a manual reverse switch. If someone upgraded it to a two-position E-unit, the wiring is essentially the same. It has a double wound motor. One wire goes from the rollers to one brush, the other brush is connected to (one end of) both fields. Two "ground" wires go from the direction switch/ e-unit tabs to each remaining end of the field (swap wires if it runs backwards/contrary to intended motion).

Thanks very much. Your information worked perfectly.