Hypothesis time! So the left of the two big boards is going to be the main controller. It has two 10-pin ribbon cables going out at the bottom as well as two 4-pin ones. These are probably the data for two rows of LCD modules (the 10-pin ones) as well as their respective alternating blinkers (the 4-pin ones).
There's also a 10-pin ribbon cable at the top, which goes to a third board which I haven't had a closer look at yet, but it looks like the power supply and backlight brightness controller.