What is this switch?

OTR your diagram didn't come through. Here's mine, you must wire it so the dist. connector hooks up as "pictured" to get phasing correct.

So on your firewall photo:

Top left should go to the female terminal of the connector which then hooks to distributor

Bottom left should go to the exposed male of that connector

Top right should go to coil NEG


Bottom right should go to coil + and to switched 12V from key

If you still use a ballast, switched 12 should go to bottom right, and one terminal of ballast should hook there, other end of ballast hooks to coil +

Module MUST sit on a nice flat surface, and MUST use thermal ('heat sink') grease. Make sure the mounting screws are grounded. I use an eyelet under one mounting screw on top of the module, and run that wire to the block.