Any one know what this is?

We just bought a 58 T Bird. Under the hood is a silver box with some electronics in it including a rheostat, that can be adjusted with a screw driver from out side the box.  There is, what appears to be a lamp cord type wire, going to the inside of the car, to a push button.  The previous owner had no idea, and said he never pushed the button.  It almost appears that it may be some sort of after market horn.  That's just a guess.

Can anyone help here?  

Thanks,

Ken