Sanwa Super Vortex - reverse?
 

Hi all. I have a "vintage" ESC called Super Vortex from Sanwa. I know nothing else about it other than it sits in a Schumacher Shotgun truck. So far I can only get it to go forward. I see no other options on it other than N H C screws, which I have tried adjusting but doesn't help. I have also tried adjusting the TH TRIM on the sender, but doesn't help either. Any tip?

Pseudo link to image (forum won't allow me to post real links):
deepbytes (dot) thronic (dot) com/misc/esc1.jpg