This is pure guess work, but possibly one of the solenoids feeds battery power to the motor to run in one direction; whilst the other solenoid feed power to the motor to run in the opposite direction.
Being a 12 volt DC motor, I would expect the motor connections from the contacts of each solenoid (Relay) to be just a mirror image of each other. Pressing the "Forward" button energises one solenoid, pressing the "Reverse" button energises the other, probably with a common negative feed to both coils. The Relays would each have double pole normally open contacts, (one for + and the other for -) to feed the motor.
As I said, pure guess work on my part.
Howard
Edited By Howard Lewis on 23/07/2016 12:58:59