I noticed when I bought my E-type that the far right rocker switch on the dash panel had no markings and was not electrically connected to anything. Looking it up in one of my books I found that this was the switch to change the headlights from high beam to low beam and back. Just what exactly were the engineers thinking? A switch that far to the right is such a hassle, reaching over there having to change the beams from high to low, etc. multiple times per trip was not very well thought out. I assume designed for the right hand side E Types. Now I know why someone installed another switch for this option on the left-hand side of the steering wheel. Much easier to get to while driving at night. Has anyone else found a handy use for this extra switch?

 

The rocker switch at far right is for the electrically heated rear window, for cars that came equipped with that ( mine did). The gauge/instrument strip is also different between Es with and without the heated rear window. The high/low beam for the headlights is the toggle switch at left of steering wheel. your second photo.

 

That rocker switch is non functioning on all late roadsters. As Valerie mentions, It's for the headed rear window in the coupes.

 

I wonder why they installed a functional switch instead of a much cheaper blanking plate. Esthetics? There are four male attachments on the back though who knows if it is original to the car.