What does this box(relay) unit do on a '68 Mustang?

[Big Block]

I have no idea what this box(relay) unit does. Can someone identify this beast and tell me what it does!
It is a metal bracket with a lip that has 2 holes in it. On the underside are the electronics, diodes and stuff proteced by a removable box which is fastened to the unit with 2 screws. There is only 1 wire coming out of this box unit and has a rubber cap on the end which fastens onto a bolt sticking out of the unit. No other wires attach to this grounded box unit.
This unit is mounted on the inside fender (passenger side) followed by the starter relay-solenoid on top of it secured by 2 bolts, washers and nuts.
Any thoughts...

 

[Mech_Engineer]

I think you need to go join www.mustangforums.com instead of asking here.

 

[HowlerMonkey]

How about a picture?

I have a 1967 stang with 428 cobra lemans with medium riser 427 intake and I still need a picture.

An educated guess would be the voltage regulator for the alternator.